diff --git a/.ci/scripts/test_synapse_port_db.sh b/.ci/scripts/test_synapse_port_db.sh
index 2b4e5ec17..50115b307 100755
--- a/.ci/scripts/test_synapse_port_db.sh
+++ b/.ci/scripts/test_synapse_port_db.sh
@@ -25,7 +25,7 @@ python -m synapse.app.homeserver --generate-keys -c .ci/sqlite-config.yaml
 echo "--- Prepare test database"
 
 # Make sure the SQLite3 database is using the latest schema and has no pending background update.
-scripts-dev/update_database --database-config .ci/sqlite-config.yaml
+scripts/update_synapse_database --database-config .ci/sqlite-config.yaml --run-background-updates
 
 # Create the PostgreSQL database.
 .ci/scripts/postgres_exec.py "CREATE DATABASE synapse"
@@ -46,7 +46,7 @@ echo "--- Prepare empty SQLite database"
 # we do this by deleting the sqlite db, and then doing the same again.
 rm .ci/test_db.db
 
-scripts-dev/update_database --database-config .ci/sqlite-config.yaml
+scripts/update_synapse_database --database-config .ci/sqlite-config.yaml --run-background-updates
 
 # re-create the PostgreSQL database.
 .ci/scripts/postgres_exec.py \
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
new file mode 100644
index 000000000..d6cd75f1d
--- /dev/null
+++ b/.github/CODEOWNERS
@@ -0,0 +1,2 @@
+# Automatically request reviews from the synapse-core team when a pull request comes in.
+* @matrix-org/synapse-core
\ No newline at end of file
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 45a1bc110..dd0e01c00 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -76,22 +76,25 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9"]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
         database: ["sqlite"]
+        toxenv: ["py"]
         include:
           # Newest Python without optional deps
-          - python-version: "3.9"
-            toxenv: "py-noextras,combine"
+          - python-version: "3.10"
+            toxenv: "py-noextras"
 
           # Oldest Python with PostgreSQL
           - python-version: "3.6"
             database: "postgres"
             postgres-version: "9.6"
+            toxenv: "py"
 
-          # Newest Python with PostgreSQL
-          - python-version: "3.9"
+          # Newest Python with newest PostgreSQL
+          - python-version: "3.10"
             database: "postgres"
-            postgres-version: "13"
+            postgres-version: "14"
+            toxenv: "py"
 
     steps:
       - uses: actions/checkout@v2
@@ -111,7 +114,7 @@ jobs:
         if: ${{ matrix.postgres-version }}
         timeout-minutes: 2
         run: until pg_isready -h localhost; do sleep 1; done
-      - run: tox -e py,combine
+      - run: tox -e ${{ matrix.toxenv }}
         env:
           TRIAL_FLAGS: "--jobs=2"
           SYNAPSE_POSTGRES: ${{ matrix.database == 'postgres' || '' }}
@@ -169,7 +172,7 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
       - run: pip install tox
-      - run: tox -e py,combine
+      - run: tox -e py
         env:
           TRIAL_FLAGS: "--jobs=2"
       - name: Dump logs
@@ -249,8 +252,8 @@ jobs:
           - python-version: "3.6"
             postgres-version: "9.6"
 
-          - python-version: "3.9"
-            postgres-version: "13"
+          - python-version: "3.10"
+            postgres-version: "14"
 
     services:
       postgres:
diff --git a/CHANGES.md b/CHANGES.md
index 3f048ba88..435387d7b 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,137 @@
+Synapse 1.45.0 (2021-10-19)
+===========================
+
+No functional changes since Synapse 1.45.0rc2.
+
+Known Issues
+------------
+
+- A suspected [performance regression](https://github.com/matrix-org/synapse/issues/11049) which was first reported after the release of 1.44.0 remains unresolved.
+
+  We have not been able to identify a probable cause. Affected users report that setting up a federation sender worker appears to alleviate symptoms of the regression.
+
+Improved Documentation
+----------------------
+
+- Reword changelog to clarify concerns about a suspected performance regression in 1.44.0. ([\#11117](https://github.com/matrix-org/synapse/issues/11117))
+
+
+Synapse 1.45.0rc2 (2021-10-14)
+==============================
+
+This release candidate [fixes](https://github.com/matrix-org/synapse/issues/11053) a user directory [bug](https://github.com/matrix-org/synapse/issues/11025) present in 1.45.0rc1.
+
+Known Issues
+------------
+
+- A suspected [performance regression](https://github.com/matrix-org/synapse/issues/11049) which was first reported after the release of 1.44.0 remains unresolved.
+
+  We have not been able to identify a probable cause. Affected users report that setting up a federation sender worker appears to alleviate symptoms of the regression.
+
+Bugfixes
+--------
+
+- Fix a long-standing bug when using multiple event persister workers where events were not correctly sent down `/sync` due to a race. ([\#11045](https://github.com/matrix-org/synapse/issues/11045))
+- Fix a bug introduced in Synapse 1.45.0rc1 where the user directory would stop updating if it processed an event from a
+  user not in the `users` table. ([\#11053](https://github.com/matrix-org/synapse/issues/11053))
+- Fix a bug introduced in Synapse 1.44.0 when logging errors during oEmbed processing. ([\#11061](https://github.com/matrix-org/synapse/issues/11061))
+
+
+Internal Changes
+----------------
+
+- Add an 'approximate difference' method to `StateFilter`. ([\#10825](https://github.com/matrix-org/synapse/issues/10825))
+- Fix inconsistent behavior of `get_last_client_by_ip` when reporting data that has not been stored in the database yet. ([\#10970](https://github.com/matrix-org/synapse/issues/10970))
+- Fix a bug introduced in Synapse 1.21.0 that causes opentracing and Prometheus metrics for replication requests to be measured incorrectly. ([\#10996](https://github.com/matrix-org/synapse/issues/10996))
+- Ensure that cache config tests do not share state. ([\#11036](https://github.com/matrix-org/synapse/issues/11036))
+
+
+Synapse 1.45.0rc1 (2021-10-12)
+==============================
+
+**Note:** Media storage providers module that read from Synapse's configuration need changes as of this version, see the [upgrade notes](https://matrix-org.github.io/synapse/develop/upgrade#upgrading-to-v1450) for more information.
+
+Known Issues
+------------
+
+- We are investigating [a performance issue](https://github.com/matrix-org/synapse/issues/11049) which was reported after the release of 1.44.0.
+- We are aware of [a bug](https://github.com/matrix-org/synapse/issues/11025) with the user directory when using application services. A second release candidate is expected which will resolve this.
+
+Features
+--------
+
+- Add [MSC3069](https://github.com/matrix-org/matrix-doc/pull/3069) support to `/account/whoami`. ([\#9655](https://github.com/matrix-org/synapse/issues/9655))
+- Support autodiscovery of oEmbed previews. ([\#10822](https://github.com/matrix-org/synapse/issues/10822))
+- Add a `user_may_send_3pid_invite` spam checker callback for modules to allow or deny 3PID invites. ([\#10894](https://github.com/matrix-org/synapse/issues/10894))
+- Add a spam checker callback to allow or deny room joins. ([\#10910](https://github.com/matrix-org/synapse/issues/10910))
+- Include an `update_synapse_database` script in the distribution. Contributed by @Fizzadar at Beeper. ([\#10954](https://github.com/matrix-org/synapse/issues/10954))
+- Include exception information in JSON logging output. Contributed by @Fizzadar at Beeper. ([\#11028](https://github.com/matrix-org/synapse/issues/11028))
+
+
+Bugfixes
+--------
+
+- Fix a minor bug in the response to `/_matrix/client/r0/voip/turnServer`. Contributed by @lukaslihotzki. ([\#10922](https://github.com/matrix-org/synapse/issues/10922))
+- Fix a bug where empty `yyyy-mm-dd/` directories would be left behind in the media store's `url_cache_thumbnails/` directory. ([\#10924](https://github.com/matrix-org/synapse/issues/10924))
+- Fix a bug introduced in Synapse v1.40.0 where the signature checks for room version 8 and 9 could be applied to earlier room versions in some situations. ([\#10927](https://github.com/matrix-org/synapse/issues/10927))
+- Fix a long-standing bug wherein deactivated users still count towards the monthly active users limit. ([\#10947](https://github.com/matrix-org/synapse/issues/10947))
+- Fix a long-standing bug which meant that events received over federation were sometimes incorrectly accepted into the room state. ([\#10956](https://github.com/matrix-org/synapse/issues/10956))
+- Fix a long-standing bug where rebuilding the user directory wouldn't exclude support and deactivated users. ([\#10960](https://github.com/matrix-org/synapse/issues/10960))
+- Fix [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) `/batch_send` endpoint rejecting subsequent batches with unknown batch ID error in existing room versions from the room creator. ([\#10962](https://github.com/matrix-org/synapse/issues/10962))
+- Fix a bug that could leak local users' per-room nicknames and avatars when the user directory is rebuilt. ([\#10981](https://github.com/matrix-org/synapse/issues/10981))
+- Fix a long-standing bug where the remainder of a batch of user directory changes would be silently dropped if the server left a room early in the batch. ([\#10982](https://github.com/matrix-org/synapse/issues/10982))
+- Correct a bugfix introduced in Synapse v1.44.0 that would catch the wrong error if a connection is lost before a response could be written to it. ([\#10995](https://github.com/matrix-org/synapse/issues/10995))
+- Fix a long-standing bug where local users' per-room nicknames/avatars were visible to anyone who could see you in the user directory. ([\#11002](https://github.com/matrix-org/synapse/issues/11002))
+- Fix a long-standing bug where a user's per-room nickname/avatar would overwrite their profile in the user directory when a room was made public. ([\#11003](https://github.com/matrix-org/synapse/issues/11003))
+- Work around a regression, introduced in Synapse v1.39.0, that caused `SynapseError`s raised by the experimental third-party rules module callback `check_event_allowed` to be ignored. ([\#11042](https://github.com/matrix-org/synapse/issues/11042))
+- Fix a bug in [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) insertion events in rooms that could cause cross-talk/conflicts between batches. ([\#10877](https://github.com/matrix-org/synapse/issues/10877))
+
+
+Improved Documentation
+----------------------
+
+- Change wording ("reference homeserver") in Synapse repository documentation. Contributed by @maxkratz. ([\#10971](https://github.com/matrix-org/synapse/issues/10971))
+- Fix a dead URL in development documentation (SAML) and change wording from "Riot" to "Element". Contributed by @maxkratz. ([\#10973](https://github.com/matrix-org/synapse/issues/10973))
+- Add additional content to the Welcome and Overview page of the documentation. ([\#10990](https://github.com/matrix-org/synapse/issues/10990))
+- Update links to MSCs in documentation. Contributed by @dklimpel. ([\#10991](https://github.com/matrix-org/synapse/issues/10991))
+
+
+Internal Changes
+----------------
+
+- Improve type hinting in `synapse.util`. ([\#10888](https://github.com/matrix-org/synapse/issues/10888))
+- Add further type hints to `synapse.storage.util`. ([\#10892](https://github.com/matrix-org/synapse/issues/10892))
+- Fix type hints to be compatible with an upcoming change to Twisted. ([\#10895](https://github.com/matrix-org/synapse/issues/10895))
+- Update utility code to handle C implementations of frozendict. ([\#10902](https://github.com/matrix-org/synapse/issues/10902))
+- Drop old functionality which maintained database compatibility with Synapse versions before v1.31. ([\#10903](https://github.com/matrix-org/synapse/issues/10903))
+- Clean-up configuration helper classes for the `ServerConfig` class. ([\#10915](https://github.com/matrix-org/synapse/issues/10915))
+- Use direct references to config flags. ([\#10916](https://github.com/matrix-org/synapse/issues/10916), [\#10959](https://github.com/matrix-org/synapse/issues/10959), [\#10985](https://github.com/matrix-org/synapse/issues/10985))
+- Clean up some of the federation event authentication code for clarity. ([\#10926](https://github.com/matrix-org/synapse/issues/10926), [\#10940](https://github.com/matrix-org/synapse/issues/10940), [\#10986](https://github.com/matrix-org/synapse/issues/10986), [\#10987](https://github.com/matrix-org/synapse/issues/10987), [\#10988](https://github.com/matrix-org/synapse/issues/10988), [\#11010](https://github.com/matrix-org/synapse/issues/11010), [\#11011](https://github.com/matrix-org/synapse/issues/11011))
+- Refactor various parts of the codebase to use `RoomVersion` objects instead of room version identifier strings. ([\#10934](https://github.com/matrix-org/synapse/issues/10934))
+- Refactor user directory tests in preparation for upcoming changes. ([\#10935](https://github.com/matrix-org/synapse/issues/10935))
+- Include the event id in the logcontext when handling PDUs received over federation. ([\#10936](https://github.com/matrix-org/synapse/issues/10936))
+- Fix logged errors in unit tests. ([\#10939](https://github.com/matrix-org/synapse/issues/10939))
+- Fix a broken test to ensure that consent configuration works during registration. ([\#10945](https://github.com/matrix-org/synapse/issues/10945))
+- Add type hints to filtering classes. ([\#10958](https://github.com/matrix-org/synapse/issues/10958))
+- Add type-hint to `HomeserverTestcase.setup_test_homeserver`. ([\#10961](https://github.com/matrix-org/synapse/issues/10961))
+- Fix the test utility function `create_room_as` so that `is_public=True` will explicitly set the `visibility` parameter of room creation requests to `public`. Contributed by @AndrewFerr. ([\#10963](https://github.com/matrix-org/synapse/issues/10963))
+- Make the release script more robust and transparent. ([\#10966](https://github.com/matrix-org/synapse/issues/10966))
+- Refactor [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) `/batch_send` mega function into smaller handler functions. ([\#10974](https://github.com/matrix-org/synapse/issues/10974))
+- Log stack traces when a missing opentracing span is detected. ([\#10983](https://github.com/matrix-org/synapse/issues/10983))
+- Update GHA config to run tests against Python 3.10 and PostgreSQL 14. ([\#10992](https://github.com/matrix-org/synapse/issues/10992))
+- Fix a long-standing bug where `ReadWriteLock`s could drop logging contexts on exit. ([\#10993](https://github.com/matrix-org/synapse/issues/10993))
+- Add a `CODEOWNERS` file to automatically request reviews from the `@matrix-org/synapse-core` team on new pull requests. ([\#10994](https://github.com/matrix-org/synapse/issues/10994))
+- Add further type hints to `synapse.state`. ([\#11004](https://github.com/matrix-org/synapse/issues/11004))
+- Remove the deprecated `BaseHandler` object. ([\#11005](https://github.com/matrix-org/synapse/issues/11005))
+- Bump mypy version for CI to 0.910, and pull in new type stubs for dependencies. ([\#11006](https://github.com/matrix-org/synapse/issues/11006))
+- Fix CI to run the unit tests without optional deps. ([\#11017](https://github.com/matrix-org/synapse/issues/11017))
+- Ensure that cache config tests do not share state. ([\#11019](https://github.com/matrix-org/synapse/issues/11019))
+- Add additional type hints to `synapse.server_notices`. ([\#11021](https://github.com/matrix-org/synapse/issues/11021))
+- Add additional type hints for `synapse.push`. ([\#11023](https://github.com/matrix-org/synapse/issues/11023))
+- When installing the optional developer dependencies, also include the dependencies needed for type-checking and unit testing. ([\#11034](https://github.com/matrix-org/synapse/issues/11034))
+- Remove unnecessary list comprehension from `synapse_port_db` to satisfy code style requirements. ([\#11043](https://github.com/matrix-org/synapse/issues/11043))
+
+
 Synapse 1.44.0 (2021-10-05)
 ===========================
 
diff --git a/README.rst b/README.rst
index 524a3a514..50de3a49b 100644
--- a/README.rst
+++ b/README.rst
@@ -55,11 +55,8 @@ solutions. The hope is for Matrix to act as the building blocks for a new
 generation of fully open and interoperable messaging and VoIP apps for the
 internet.
 
-Synapse is a reference "homeserver" implementation of Matrix from the core
-development team at matrix.org, written in Python/Twisted.  It is intended to
-showcase the concept of Matrix and let folks see the spec in the context of a
-codebase and let you run your own homeserver and generally help bootstrap the
-ecosystem.
+Synapse is a Matrix "homeserver" implementation developed by the matrix.org core 
+team, written in Python 3/Twisted.
 
 In Matrix, every user runs one or more Matrix clients, which connect through to
 a Matrix homeserver. The homeserver stores all their personal chat history and
@@ -301,7 +298,7 @@ to install using pip and a virtualenv::
 
     python3 -m venv ./env
     source ./env/bin/activate
-    pip install -e ".[all,test]"
+    pip install -e ".[all,dev]"
 
 This will run a process of downloading and installing all the needed
 dependencies into a virtual env. If any dependencies fail to install,
diff --git a/debian/changelog b/debian/changelog
index 9e878fbc2..5fefb2f2a 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,25 @@
+matrix-synapse-py3 (1.45.0) stable; urgency=medium
+
+  * New synapse release 1.45.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 19 Oct 2021 11:18:53 +0100
+
+matrix-synapse-py3 (1.45.0~rc2) stable; urgency=medium
+
+  * New synapse release 1.45.0~rc2.
+
+ -- Synapse Packaging team <packages@matrix.org>  Thu, 14 Oct 2021 10:58:24 +0100
+
+matrix-synapse-py3 (1.45.0~rc1) stable; urgency=medium
+
+  [ Nick @ Beeper ]
+  * Include an `update_synapse_database` script in the distribution.
+
+  [ Synapse Packaging team ]
+  * New synapse release 1.45.0~rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 12 Oct 2021 10:46:27 +0100
+
 matrix-synapse-py3 (1.44.0) stable; urgency=medium
 
   * New synapse release 1.44.0.
diff --git a/debian/matrix-synapse-py3.links b/debian/matrix-synapse-py3.links
index 53e296541..7eeba180d 100644
--- a/debian/matrix-synapse-py3.links
+++ b/debian/matrix-synapse-py3.links
@@ -3,3 +3,4 @@ opt/venvs/matrix-synapse/bin/register_new_matrix_user usr/bin/register_new_matri
 opt/venvs/matrix-synapse/bin/synapse_port_db usr/bin/synapse_port_db
 opt/venvs/matrix-synapse/bin/synapse_review_recent_signups usr/bin/synapse_review_recent_signups
 opt/venvs/matrix-synapse/bin/synctl usr/bin/synctl
+opt/venvs/matrix-synapse/bin/update_synapse_database usr/bin/update_synapse_database
diff --git a/docs/MSC1711_certificates_FAQ.md b/docs/MSC1711_certificates_FAQ.md
index 7d71c190a..086899a9d 100644
--- a/docs/MSC1711_certificates_FAQ.md
+++ b/docs/MSC1711_certificates_FAQ.md
@@ -3,7 +3,7 @@
 ## Historical Note
 This document was originally written to guide server admins through the upgrade
 path towards Synapse 1.0. Specifically,
-[MSC1711](https://github.com/matrix-org/matrix-doc/blob/master/proposals/1711-x509-for-federation.md)
+[MSC1711](https://github.com/matrix-org/matrix-doc/blob/main/proposals/1711-x509-for-federation.md)
 required that all servers present valid TLS certificates on their federation
 API. Admins were encouraged to achieve compliance from version 0.99.0 (released
 in February 2019) ahead of version 1.0 (released June 2019) enforcing the
@@ -282,7 +282,7 @@ coffin of the Perspectives project (which was already pretty dead). So, the
 Spec Core Team decided that a better approach would be to mandate valid TLS
 certificates for federation alongside the rest of the Web. More details can be
 found in
-[MSC1711](https://github.com/matrix-org/matrix-doc/blob/master/proposals/1711-x509-for-federation.md#background-the-failure-of-the-perspectives-approach).
+[MSC1711](https://github.com/matrix-org/matrix-doc/blob/main/proposals/1711-x509-for-federation.md#background-the-failure-of-the-perspectives-approach).
 
 This results in a breaking change, which is disruptive, but absolutely critical
 for the security model. However, the existence of Let's Encrypt as a trivial
diff --git a/docs/README.md b/docs/README.md
index e113f55d2..6d70f5aff 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -6,9 +6,9 @@ Please update any links to point to the new website instead.
 ## About
 
 This directory currently holds a series of markdown files documenting how to install, use
-and develop Synapse, the reference Matrix homeserver. The documentation is readable directly
-from this repository, but it is recommended to instead browse through the
-[website](https://matrix-org.github.io/synapse) for easier discoverability.
+and develop Synapse. The documentation is readable directly from this repository, but it is 
+recommended to instead browse through the [website](https://matrix-org.github.io/synapse) for 
+easier discoverability.
 
 ## Adding to the documentation
 
diff --git a/docs/development/contributing_guide.md b/docs/development/contributing_guide.md
index 713366368..3bf08a72b 100644
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -50,7 +50,7 @@ setup a *virtualenv*, as follows:
 cd path/where/you/have/cloned/the/repository
 python3 -m venv ./env
 source ./env/bin/activate
-pip install -e ".[all,lint,mypy,test]"
+pip install -e ".[all,dev]"
 pip install tox
 ```
 
@@ -63,7 +63,7 @@ TBD
 
 # 5. Get in touch.
 
-Join our developer community on Matrix: #synapse-dev:matrix.org !
+Join our developer community on Matrix: [#synapse-dev:matrix.org](https://matrix.to/#/#synapse-dev:matrix.org)!
 
 
 # 6. Pick an issue.
diff --git a/docs/development/saml.md b/docs/development/saml.md
index a9bfd2dc0..60a431d68 100644
--- a/docs/development/saml.md
+++ b/docs/development/saml.md
@@ -1,10 +1,9 @@
 # How to test SAML as a developer without a server
 
-https://capriza.github.io/samling/samling.html (https://github.com/capriza/samling) is a great
-resource for being able to tinker with the SAML options within Synapse without needing to
-deploy and configure a complicated software stack.
+https://fujifish.github.io/samling/samling.html (https://github.com/fujifish/samling) is a great resource for being able to tinker with the 
+SAML options within Synapse without needing to deploy and configure a complicated software stack.
 
-To make Synapse (and therefore Riot) use it:
+To make Synapse (and therefore Element) use it:
 
 1. Use the samling.html URL above or deploy your own and visit the IdP Metadata tab.
 2. Copy the XML to your clipboard.
@@ -26,9 +25,9 @@ To make Synapse (and therefore Riot) use it:
    the dependencies are installed and ready to go.
 7. Restart Synapse.
 
-Then in Riot:
+Then in Element:
 
-1. Visit the login page with a Riot pointing at your homeserver.
+1. Visit the login page and point Element towards your homeserver using the `public_baseurl` above.
 2. Click the Single Sign-On button.
 3. On the samling page, enter a Name Identifier and add a SAML Attribute for `uid=your_localpart`.
    The response must also be signed.
diff --git a/docs/modules/spam_checker_callbacks.md b/docs/modules/spam_checker_callbacks.md
index 7920ac5f8..787e99074 100644
--- a/docs/modules/spam_checker_callbacks.md
+++ b/docs/modules/spam_checker_callbacks.md
@@ -19,6 +19,21 @@ either a `bool` to indicate whether the event must be rejected because of spam,
 to indicate the event must be rejected because of spam and to give a rejection reason to
 forward to clients.
 
+### `user_may_join_room`
+
+```python
+async def user_may_join_room(user: str, room: str, is_invited: bool) -> bool
+```
+
+Called when a user is trying to join a room. The module must return a `bool` to indicate
+whether the user can join the room. The user is represented by their Matrix user ID (e.g.
+`@alice:example.com`) and the room is represented by its Matrix ID (e.g.
+`!room:example.com`). The module is also given a boolean to indicate whether the user
+currently has a pending invite in the room.
+
+This callback isn't called if the join is performed by a server administrator, or in the
+context of a room creation.
+
 ### `user_may_invite`
 
 ```python
@@ -29,6 +44,41 @@ Called when processing an invitation. The module must return a `bool` indicating
 the inviter can invite the invitee to the given room. Both inviter and invitee are
 represented by their Matrix user ID (e.g. `@alice:example.com`).
 
+### `user_may_send_3pid_invite`
+
+```python
+async def user_may_send_3pid_invite(
+    inviter: str,
+    medium: str,
+    address: str,
+    room_id: str,
+) -> bool
+```
+
+Called when processing an invitation using a third-party identifier (also called a 3PID,
+e.g. an email address or a phone number). The module must return a `bool` indicating
+whether the inviter can invite the invitee to the given room.
+
+The inviter is represented by their Matrix user ID (e.g. `@alice:example.com`), and the
+invitee is represented by its medium (e.g. "email") and its address
+(e.g. `alice@example.com`). See [the Matrix specification](https://matrix.org/docs/spec/appendices#pid-types)
+for more information regarding third-party identifiers.
+
+For example, a call to this callback to send an invitation to the email address
+`alice@example.com` would look like this:
+
+```python
+await user_may_send_3pid_invite(
+    "@bob:example.com",  # The inviter's user ID
+    "email",  # The medium of the 3PID to invite
+    "alice@example.com",  # The address of the 3PID to invite
+    "!some_room:example.com",  # The ID of the room to send the invite into
+)
+```
+
+**Note**: If the third-party identifier is already associated with a matrix user ID,
+[`user_may_invite`](#user_may_invite) will be used instead.
+
 ### `user_may_create_room`
 
 ```python
diff --git a/docs/upgrade.md b/docs/upgrade.md
index a8221372d..18ecb2678 100644
--- a/docs/upgrade.md
+++ b/docs/upgrade.md
@@ -85,6 +85,15 @@ process, for example:
     dpkg -i matrix-synapse-py3_1.3.0+stretch1_amd64.deb
     ```
 
+# Upgrading to v1.45.0
+
+## Changes required to media storage provider modules when reading from the Synapse configuration object
+
+Media storage provider modules that read from the Synapse configuration object (i.e. that
+read the value of `hs.config.[...]`) now need to specify the configuration section they're
+reading from. This means that if a module reads the value of e.g. `hs.config.media_store_path`,
+it needs to replace it with `hs.config.media.media_store_path`.
+
 # Upgrading to v1.44.0
 
 ## The URL preview cache is no longer mirrored to storage providers
diff --git a/docs/usage/administration/admin_api/registration_tokens.md b/docs/usage/administration/admin_api/registration_tokens.md
index 828c0277d..c48d060dc 100644
--- a/docs/usage/administration/admin_api/registration_tokens.md
+++ b/docs/usage/administration/admin_api/registration_tokens.md
@@ -1,7 +1,8 @@
 # Registration Tokens
 
 This API allows you to manage tokens which can be used to authenticate
-registration requests, as proposed in [MSC3231](https://github.com/govynnus/matrix-doc/blob/token-registration/proposals/3231-token-authenticated-registration.md).
+registration requests, as proposed in
+[MSC3231](https://github.com/matrix-org/matrix-doc/blob/main/proposals/3231-token-authenticated-registration.md).
 To use it, you will need to enable the `registration_requires_token` config
 option, and authenticate by providing an `access_token` for a server admin:
 see [Admin API](../../usage/administration/admin_api).
diff --git a/docs/welcome_and_overview.md b/docs/welcome_and_overview.md
index 30e75984d..aab2d6b4f 100644
--- a/docs/welcome_and_overview.md
+++ b/docs/welcome_and_overview.md
@@ -1,4 +1,79 @@
 # Introduction
 
-Welcome to the documentation repository for Synapse, the reference
-[Matrix](https://matrix.org) homeserver implementation.
\ No newline at end of file
+Welcome to the documentation repository for Synapse, a 
+[Matrix](https://matrix.org) homeserver implementation developed by the matrix.org core 
+team.
+
+## Installing and using Synapse
+
+This documentation covers topics for **installation**, **configuration** and
+**maintainence** of your Synapse process:
+
+* Learn how to [install](setup/installation.md) and
+  [configure](usage/configuration/index.html) your own instance, perhaps with [Single
+  Sign-On](usage/configuration/user_authentication/index.html).
+
+* See how to [upgrade](upgrade.md) between Synapse versions.
+
+* Administer your instance using the [Admin
+  API](usage/administration/admin_api/index.html), installing [pluggable
+  modules](modules/index.html), or by accessing the [manhole](manhole.md).
+
+* Learn how to [read log lines](usage/administration/request_log.md), configure
+  [logging](usage/configuration/logging_sample_config.md) or set up [structured
+  logging](structured_logging.md).
+
+* Scale Synapse through additional [worker processes](workers.md).
+
+* Set up [monitoring and metrics](metrics-howto.md) to keep an eye on your
+  Synapse instance's performance.
+
+## Developing on Synapse
+
+Contributions are welcome! Synapse is primarily written in
+[Python](https://python.org). As a developer, you may be interested in the
+following documentation:
+
+* Read the [Contributing Guide](development/contributing_guide.md). It is meant
+  to walk new contributors through the process of developing and submitting a
+  change to the Synapse codebase (which is [hosted on
+  GitHub](https://github.com/matrix-org/synapse)).
+
+* Set up your [development
+  environment](development/contributing_guide.md#2-what-do-i-need), then learn
+  how to [lint](development/contributing_guide.md#run-the-linters) and
+  [test](development/contributing_guide.md#8-test-test-test) your code.
+
+* Look at [the issue tracker](https://github.com/matrix-org/synapse/issues) for
+  bugs to fix or features to add. If you're new, it may be best to start with
+  those labeled [good first
+  issue](https://github.com/matrix-org/synapse/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22).
+
+* Understand [how Synapse is
+  built](development/internal_documentation/index.html), how to [migrate
+  database schemas](development/database_schema.md), learn about
+  [federation](federate.md) and how to [set up a local
+  federation](federate.md#running-a-demo-federation-of-synapses) for development.
+
+* We like to keep our `git` history clean. [Learn](development/git.md) how to
+  do so!
+
+* And finally, contribute to this documentation! The source for which is
+  [located here](https://github.com/matrix-org/synapse/tree/develop/docs).
+
+## Donating to Synapse development
+
+Want to help keep Synapse going but don't know how to code? Synapse is a
+[Matrix.org Foundation](https://matrix.org) project. Consider becoming a
+supportor on [Liberapay](https://liberapay.com/matrixdotorg),
+[Patreon](https://patreon.com/matrixdotorg) or through
+[PayPal](https://paypal.me/matrixdotorg) via a one-time donation.
+
+If you are an organisation or enterprise and would like to sponsor development,
+reach out to us over email at: support (at) matrix.org
+
+## Reporting a security vulnerability
+
+If you've found a security issue in Synapse or any other Matrix.org Foundation
+project, please report it to us in accordance with our [Security Disclosure
+Policy](https://www.matrix.org/security-disclosure-policy/). Thank you!
diff --git a/mypy.ini b/mypy.ini
index 437d0a46a..a7019e2bd 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -96,15 +96,48 @@ files =
 [mypy-synapse.handlers.*]
 disallow_untyped_defs = True
 
+[mypy-synapse.push.*]
+disallow_untyped_defs = True
+
 [mypy-synapse.rest.*]
 disallow_untyped_defs = True
 
+[mypy-synapse.server_notices.*]
+disallow_untyped_defs = True
+
+[mypy-synapse.state.*]
+disallow_untyped_defs = True
+
+[mypy-synapse.storage.util.*]
+disallow_untyped_defs = True
+
+[mypy-synapse.streams.*]
+disallow_untyped_defs = True
+
 [mypy-synapse.util.batching_queue]
 disallow_untyped_defs = True
 
+[mypy-synapse.util.caches.cached_call]
+disallow_untyped_defs = True
+
 [mypy-synapse.util.caches.dictionary_cache]
 disallow_untyped_defs = True
 
+[mypy-synapse.util.caches.lrucache]
+disallow_untyped_defs = True
+
+[mypy-synapse.util.caches.response_cache]
+disallow_untyped_defs = True
+
+[mypy-synapse.util.caches.stream_change_cache]
+disallow_untyped_defs = True
+
+[mypy-synapse.util.caches.ttl_cache]
+disallow_untyped_defs = True
+
+[mypy-synapse.util.daemonize]
+disallow_untyped_defs = True
+
 [mypy-synapse.util.file_consumer]
 disallow_untyped_defs = True
 
@@ -141,6 +174,9 @@ disallow_untyped_defs = True
 [mypy-synapse.util.msisdn]
 disallow_untyped_defs = True
 
+[mypy-synapse.util.patch_inline_callbacks]
+disallow_untyped_defs = True
+
 [mypy-synapse.util.ratelimitutils]
 disallow_untyped_defs = True
 
@@ -162,98 +198,106 @@ disallow_untyped_defs = True
 [mypy-synapse.util.wheel_timer]
 disallow_untyped_defs = True
 
-[mypy-pymacaroons.*]
-ignore_missing_imports = True
+[mypy-synapse.util.versionstring]
+disallow_untyped_defs = True
 
-[mypy-zope]
-ignore_missing_imports = True
+[mypy-tests.handlers.test_user_directory]
+disallow_untyped_defs = True
 
-[mypy-bcrypt]
-ignore_missing_imports = True
+[mypy-tests.storage.test_user_directory]
+disallow_untyped_defs = True
 
-[mypy-constantly]
-ignore_missing_imports = True
+;; Dependencies without annotations
+;; Before ignoring a module, check to see if type stubs are available.
+;; The `typeshed` project maintains stubs here:
+;;     https://github.com/python/typeshed/tree/master/stubs
+;; and for each package `foo` there's a corresponding `types-foo` package on PyPI,
+;; which we can pull in as a dev dependency by adding to `setup.py`'s
+;; `CONDITIONAL_REQUIREMENTS["mypy"]` list.
 
-[mypy-twisted.*]
+[mypy-authlib.*]
 ignore_missing_imports = True
 
-[mypy-treq.*]
+[mypy-bcrypt]
 ignore_missing_imports = True
 
-[mypy-hyperlink]
+[mypy-canonicaljson]
 ignore_missing_imports = True
 
-[mypy-h11]
+[mypy-constantly]
 ignore_missing_imports = True
 
-[mypy-msgpack]
+[mypy-daemonize]
 ignore_missing_imports = True
 
-[mypy-opentracing]
+[mypy-h11]
 ignore_missing_imports = True
 
-[mypy-OpenSSL.*]
+[mypy-hiredis]
 ignore_missing_imports = True
 
-[mypy-netaddr]
+[mypy-hyperlink]
 ignore_missing_imports = True
 
-[mypy-saml2.*]
+[mypy-ijson.*]
 ignore_missing_imports = True
 
-[mypy-canonicaljson]
+[mypy-jaeger_client.*]
 ignore_missing_imports = True
 
-[mypy-jaeger_client.*]
+[mypy-josepy.*]
 ignore_missing_imports = True
 
-[mypy-jsonschema]
+[mypy-jwt.*]
 ignore_missing_imports = True
 
-[mypy-signedjson.*]
+[mypy-lxml]
 ignore_missing_imports = True
 
-[mypy-prometheus_client.*]
+[mypy-msgpack]
 ignore_missing_imports = True
 
-[mypy-service_identity.*]
+[mypy-nacl.*]
 ignore_missing_imports = True
 
-[mypy-daemonize]
+[mypy-netaddr]
 ignore_missing_imports = True
 
-[mypy-sentry_sdk]
+[mypy-opentracing]
 ignore_missing_imports = True
 
-[mypy-PIL.*]
+[mypy-phonenumbers.*]
 ignore_missing_imports = True
 
-[mypy-lxml]
+[mypy-prometheus_client.*]
 ignore_missing_imports = True
 
-[mypy-jwt.*]
+[mypy-pymacaroons.*]
 ignore_missing_imports = True
 
-[mypy-authlib.*]
+[mypy-pympler.*]
 ignore_missing_imports = True
 
 [mypy-rust_python_jaeger_reporter.*]
 ignore_missing_imports = True
 
-[mypy-nacl.*]
+[mypy-saml2.*]
 ignore_missing_imports = True
 
-[mypy-hiredis]
+[mypy-sentry_sdk]
 ignore_missing_imports = True
 
-[mypy-josepy.*]
+[mypy-service_identity.*]
 ignore_missing_imports = True
 
-[mypy-pympler.*]
+[mypy-signedjson.*]
 ignore_missing_imports = True
 
-[mypy-phonenumbers.*]
+[mypy-treq.*]
 ignore_missing_imports = True
 
-[mypy-ijson.*]
+[mypy-twisted.*]
+ignore_missing_imports = True
+
+[mypy-zope]
 ignore_missing_imports = True
diff --git a/scripts-dev/lint.sh b/scripts-dev/lint.sh
index 809eff166..b6554a73c 100755
--- a/scripts-dev/lint.sh
+++ b/scripts-dev/lint.sh
@@ -90,10 +90,10 @@ else
           "scripts/hash_password"
           "scripts/register_new_matrix_user"
           "scripts/synapse_port_db"
+          "scripts/update_synapse_database"
           "scripts-dev"
           "scripts-dev/build_debian_packages"
           "scripts-dev/sign_json"
-          "scripts-dev/update_database"
           "contrib" "synctl" "setup.py" "synmark" "stubs" ".ci"
       )
   fi
diff --git a/scripts-dev/make_full_schema.sh b/scripts-dev/make_full_schema.sh
index 39bf30d25..c3c90f4ec 100755
--- a/scripts-dev/make_full_schema.sh
+++ b/scripts-dev/make_full_schema.sh
@@ -147,7 +147,7 @@ python -m synapse.app.homeserver --generate-keys -c "$SQLITE_CONFIG"
 
 # Make sure the SQLite3 database is using the latest schema and has no pending background update.
 echo "Running db background jobs..."
-scripts-dev/update_database --database-config "$SQLITE_CONFIG"
+scripts/update_synapse_database --database-config --run-background-updates "$SQLITE_CONFIG"
 
 # Create the PostgreSQL database.
 echo "Creating postgres database..."
diff --git a/scripts-dev/release.py b/scripts-dev/release.py
index ab2d860ab..4e1f99fee 100755
--- a/scripts-dev/release.py
+++ b/scripts-dev/release.py
@@ -35,6 +35,19 @@
 from packaging import version
 
 
+def run_until_successful(command, *args, **kwargs):
+    while True:
+        completed_process = subprocess.run(command, *args, **kwargs)
+        exit_code = completed_process.returncode
+        if exit_code == 0:
+            # successful, so nothing more to do here.
+            return completed_process
+
+        print(f"The command {command!r} failed with exit code {exit_code}.")
+        print("Please try to correct the failure and then re-run.")
+        click.confirm("Try again?", abort=True)
+
+
 @click.group()
 def cli():
     """An interactive script to walk through the parts of creating a release.
@@ -197,7 +210,7 @@ def prepare():
         f.write(parsed_synapse_ast.dumps())
 
     # Generate changelogs
-    subprocess.run("python3 -m towncrier", shell=True)
+    run_until_successful("python3 -m towncrier", shell=True)
 
     # Generate debian changelogs
     if parsed_new_version.pre is not None:
@@ -209,11 +222,11 @@ def prepare():
     else:
         debian_version = new_version
 
-    subprocess.run(
+    run_until_successful(
         f'dch -M -v {debian_version} "New synapse release {debian_version}."',
         shell=True,
     )
-    subprocess.run('dch -M -r -D stable ""', shell=True)
+    run_until_successful('dch -M -r -D stable ""', shell=True)
 
     # Show the user the changes and ask if they want to edit the change log.
     repo.git.add("-u")
@@ -224,7 +237,7 @@ def prepare():
 
     # Commit the changes.
     repo.git.add("-u")
-    repo.git.commit(f"-m {new_version}")
+    repo.git.commit("-m", new_version)
 
     # We give the option to bail here in case the user wants to make sure things
     # are OK before pushing.
@@ -239,6 +252,8 @@ def prepare():
     # Otherwise, push and open the changelog in the browser.
     repo.git.push("-u", repo.remote().name, repo.active_branch.name)
 
+    print("Opening the changelog in your browser...")
+    print("Please ask others to give it a check.")
     click.launch(
         f"https://github.com/matrix-org/synapse/blob/{repo.active_branch.name}/CHANGES.md"
     )
@@ -290,7 +305,19 @@ def tag(gh_token: Optional[str]):
 
     # If no token was given, we bail here
     if not gh_token:
+        print("Launching the GitHub release page in your browser.")
+        print("Please correct the title and create a draft.")
+        if current_version.is_prerelease:
+            print("As this is an RC, remember to mark it as a pre-release!")
+        print("(by the way, this step can be automated by passing --gh-token,")
+        print("or one of the GH_TOKEN or GITHUB_TOKEN env vars.)")
         click.launch(f"https://github.com/matrix-org/synapse/releases/edit/{tag_name}")
+
+        print("Once done, you need to wait for the release assets to build.")
+        if click.confirm("Launch the release assets actions page?", default=True):
+            click.launch(
+                f"https://github.com/matrix-org/synapse/actions?query=branch%3A{tag_name}"
+            )
         return
 
     # Create a new draft release
@@ -305,6 +332,7 @@ def tag(gh_token: Optional[str]):
     )
 
     # Open the release and the actions where we are building the assets.
+    print("Launching the release page and the actions page.")
     click.launch(release.html_url)
     click.launch(
         f"https://github.com/matrix-org/synapse/actions?query=branch%3A{tag_name}"
diff --git a/scripts/synapse_port_db b/scripts/synapse_port_db
index b31c3762b..5346ccc82 100755
--- a/scripts/synapse_port_db
+++ b/scripts/synapse_port_db
@@ -217,7 +217,7 @@ class MockHomeserver:
     def __init__(self, config):
         self.clock = Clock(reactor)
         self.config = config
-        self.hostname = config.server_name
+        self.hostname = config.server.server_name
         self.version_string = "Synapse/" + get_version_string(synapse)
 
     def get_clock(self):
@@ -585,7 +585,7 @@ class Porter(object):
                 return
 
             self.postgres_store = self.build_db_store(
-                self.hs_config.get_single_database()
+                self.hs_config.database.get_single_database()
             )
 
             await self.run_background_updates_on_postgres()
@@ -1071,7 +1071,7 @@ class CursesProgress(Progress):
 
         self.stdscr.addstr(0, 0, status, curses.A_BOLD)
 
-        max_len = max([len(t) for t in self.tables.keys()])
+        max_len = max(len(t) for t in self.tables.keys())
 
         left_margin = 5
         middle_space = 1
diff --git a/scripts-dev/update_database b/scripts/update_synapse_database
similarity index 84%
rename from scripts-dev/update_database
rename to scripts/update_synapse_database
index 87f709b6e..6c088bad9 100755
--- a/scripts-dev/update_database
+++ b/scripts/update_synapse_database
@@ -36,16 +36,35 @@ class MockHomeserver(HomeServer):
 
     def __init__(self, config, **kwargs):
         super(MockHomeserver, self).__init__(
-            config.server_name, reactor=reactor, config=config, **kwargs
+            config.server.server_name, reactor=reactor, config=config, **kwargs
         )
 
         self.version_string = "Synapse/" + get_version_string(synapse)
 
 
-if __name__ == "__main__":
+def run_background_updates(hs):
+    store = hs.get_datastore()
+
+    async def run_background_updates():
+        await store.db_pool.updates.run_background_updates(sleep=False)
+        # Stop the reactor to exit the script once every background update is run.
+        reactor.stop()
+
+    def run():
+        # Apply all background updates on the database.
+        defer.ensureDeferred(
+            run_as_background_process("background_updates", run_background_updates)
+        )
+
+    reactor.callWhenRunning(run)
+
+    reactor.run()
+
+
+def main():
     parser = argparse.ArgumentParser(
         description=(
-            "Updates a synapse database to the latest schema and runs background updates"
+            "Updates a synapse database to the latest schema and optionally runs background updates"
             " on it."
         )
     )
@@ -54,7 +73,13 @@ if __name__ == "__main__":
         "--database-config",
         type=argparse.FileType("r"),
         required=True,
-        help="A database config file for either a SQLite3 database or a PostgreSQL one.",
+        help="Synapse configuration file, giving the details of the database to be updated",
+    )
+    parser.add_argument(
+        "--run-background-updates",
+        action="store_true",
+        required=False,
+        help="run background updates after upgrading the database schema",
     )
 
     args = parser.parse_args()
@@ -82,19 +107,10 @@ if __name__ == "__main__":
     # Setup instantiates the store within the homeserver object and updates the
     # DB.
     hs.setup()
-    store = hs.get_datastore()
 
-    async def run_background_updates():
-        await store.db_pool.updates.run_background_updates(sleep=False)
-        # Stop the reactor to exit the script once every background update is run.
-        reactor.stop()
+    if args.run_background_updates:
+        run_background_updates(hs)
 
-    def run():
-        # Apply all background updates on the database.
-        defer.ensureDeferred(
-            run_as_background_process("background_updates", run_background_updates)
-        )
 
-    reactor.callWhenRunning(run)
-
-    reactor.run()
+if __name__ == "__main__":
+    main()
diff --git a/setup.py b/setup.py
index c47856351..220084a49 100755
--- a/setup.py
+++ b/setup.py
@@ -103,17 +103,17 @@ def exec_file(path_segments):
     "flake8",
 ]
 
-CONDITIONAL_REQUIREMENTS["dev"] = CONDITIONAL_REQUIREMENTS["lint"] + [
-    # The following are used by the release script
-    "click==7.1.2",
-    "redbaron==0.9.2",
-    "GitPython==3.1.14",
-    "commonmark==0.9.1",
-    "pygithub==1.55",
+CONDITIONAL_REQUIREMENTS["mypy"] = [
+    "mypy==0.910",
+    "mypy-zope==0.3.2",
+    "types-bleach>=4.1.0",
+    "types-jsonschema>=3.2.0",
+    "types-Pillow>=8.3.4",
+    "types-pyOpenSSL>=20.0.7",
+    "types-PyYAML>=5.4.10",
+    "types-setuptools>=57.4.0",
 ]
 
-CONDITIONAL_REQUIREMENTS["mypy"] = ["mypy==0.812", "mypy-zope==0.2.13"]
-
 # Dependencies which are exclusively required by unit test code. This is
 # NOT a list of all modules that are necessary to run the unit tests.
 # Tests assume that all optional dependencies are installed.
@@ -121,6 +121,20 @@ def exec_file(path_segments):
 # parameterized_class decorator was introduced in parameterized 0.7.0
 CONDITIONAL_REQUIREMENTS["test"] = ["parameterized>=0.7.0"]
 
+CONDITIONAL_REQUIREMENTS["dev"] = (
+    CONDITIONAL_REQUIREMENTS["lint"]
+    + CONDITIONAL_REQUIREMENTS["mypy"]
+    + CONDITIONAL_REQUIREMENTS["test"]
+    + [
+        # The following are used by the release script
+        "click==7.1.2",
+        "redbaron==0.9.2",
+        "GitPython==3.1.14",
+        "commonmark==0.9.1",
+        "pygithub==1.55",
+    ]
+)
+
 setup(
     name="matrix-synapse",
     version=version,
diff --git a/synapse/__init__.py b/synapse/__init__.py
index b8979c365..97452f34f 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -47,7 +47,7 @@
 except ImportError:
     pass
 
-__version__ = "1.44.0"
+__version__ = "1.45.0"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when
diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index ad1ff6a9d..20e91a115 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -15,7 +15,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import json
-from typing import List
+from typing import (
+    TYPE_CHECKING,
+    Awaitable,
+    Container,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    TypeVar,
+    Union,
+)
 
 import jsonschema
 from jsonschema import FormatChecker
@@ -23,7 +33,11 @@
 from synapse.api.constants import EventContentFields
 from synapse.api.errors import SynapseError
 from synapse.api.presence import UserPresenceState
-from synapse.types import RoomID, UserID
+from synapse.events import EventBase
+from synapse.types import JsonDict, RoomID, UserID
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
 
 FILTER_SCHEMA = {
     "additionalProperties": False,
@@ -120,25 +134,29 @@
 
 
 @FormatChecker.cls_checks("matrix_room_id")
-def matrix_room_id_validator(room_id_str):
+def matrix_room_id_validator(room_id_str: str) -> RoomID:
     return RoomID.from_string(room_id_str)
 
 
 @FormatChecker.cls_checks("matrix_user_id")
-def matrix_user_id_validator(user_id_str):
+def matrix_user_id_validator(user_id_str: str) -> UserID:
     return UserID.from_string(user_id_str)
 
 
 class Filtering:
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.store = hs.get_datastore()
 
-    async def get_user_filter(self, user_localpart, filter_id):
+    async def get_user_filter(
+        self, user_localpart: str, filter_id: Union[int, str]
+    ) -> "FilterCollection":
         result = await self.store.get_user_filter(user_localpart, filter_id)
         return FilterCollection(result)
 
-    def add_user_filter(self, user_localpart, user_filter):
+    def add_user_filter(
+        self, user_localpart: str, user_filter: JsonDict
+    ) -> Awaitable[int]:
         self.check_valid_filter(user_filter)
         return self.store.add_user_filter(user_localpart, user_filter)
 
@@ -146,13 +164,13 @@ def add_user_filter(self, user_localpart, user_filter):
     #   replace_user_filter at some point? There's no REST API specified for
     #   them however
 
-    def check_valid_filter(self, user_filter_json):
+    def check_valid_filter(self, user_filter_json: JsonDict) -> None:
         """Check if the provided filter is valid.
 
         This inspects all definitions contained within the filter.
 
         Args:
-            user_filter_json(dict): The filter
+            user_filter_json: The filter
         Raises:
             SynapseError: If the filter is not valid.
         """
@@ -167,8 +185,12 @@ def check_valid_filter(self, user_filter_json):
             raise SynapseError(400, str(e))
 
 
+# Filters work across events, presence EDUs, and account data.
+FilterEvent = TypeVar("FilterEvent", EventBase, UserPresenceState, JsonDict)
+
+
 class FilterCollection:
-    def __init__(self, filter_json):
+    def __init__(self, filter_json: JsonDict):
         self._filter_json = filter_json
 
         room_filter_json = self._filter_json.get("room", {})
@@ -188,25 +210,25 @@ def __init__(self, filter_json):
         self.event_fields = filter_json.get("event_fields", [])
         self.event_format = filter_json.get("event_format", "client")
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return "<FilterCollection %s>" % (json.dumps(self._filter_json),)
 
-    def get_filter_json(self):
+    def get_filter_json(self) -> JsonDict:
         return self._filter_json
 
-    def timeline_limit(self):
+    def timeline_limit(self) -> int:
         return self._room_timeline_filter.limit()
 
-    def presence_limit(self):
+    def presence_limit(self) -> int:
         return self._presence_filter.limit()
 
-    def ephemeral_limit(self):
+    def ephemeral_limit(self) -> int:
         return self._room_ephemeral_filter.limit()
 
-    def lazy_load_members(self):
+    def lazy_load_members(self) -> bool:
         return self._room_state_filter.lazy_load_members()
 
-    def include_redundant_members(self):
+    def include_redundant_members(self) -> bool:
         return self._room_state_filter.include_redundant_members()
 
     def filter_presence(self, events):
@@ -218,29 +240,31 @@ def filter_account_data(self, events):
     def filter_room_state(self, events):
         return self._room_state_filter.filter(self._room_filter.filter(events))
 
-    def filter_room_timeline(self, events):
+    def filter_room_timeline(self, events: Iterable[FilterEvent]) -> List[FilterEvent]:
         return self._room_timeline_filter.filter(self._room_filter.filter(events))
 
-    def filter_room_ephemeral(self, events):
+    def filter_room_ephemeral(self, events: Iterable[FilterEvent]) -> List[FilterEvent]:
         return self._room_ephemeral_filter.filter(self._room_filter.filter(events))
 
-    def filter_room_account_data(self, events):
+    def filter_room_account_data(
+        self, events: Iterable[FilterEvent]
+    ) -> List[FilterEvent]:
         return self._room_account_data.filter(self._room_filter.filter(events))
 
-    def blocks_all_presence(self):
+    def blocks_all_presence(self) -> bool:
         return (
             self._presence_filter.filters_all_types()
             or self._presence_filter.filters_all_senders()
         )
 
-    def blocks_all_room_ephemeral(self):
+    def blocks_all_room_ephemeral(self) -> bool:
         return (
             self._room_ephemeral_filter.filters_all_types()
             or self._room_ephemeral_filter.filters_all_senders()
             or self._room_ephemeral_filter.filters_all_rooms()
         )
 
-    def blocks_all_room_timeline(self):
+    def blocks_all_room_timeline(self) -> bool:
         return (
             self._room_timeline_filter.filters_all_types()
             or self._room_timeline_filter.filters_all_senders()
@@ -249,7 +273,7 @@ def blocks_all_room_timeline(self):
 
 
 class Filter:
-    def __init__(self, filter_json):
+    def __init__(self, filter_json: JsonDict):
         self.filter_json = filter_json
 
         self.types = self.filter_json.get("types", None)
@@ -266,20 +290,20 @@ def __init__(self, filter_json):
         self.labels = self.filter_json.get("org.matrix.labels", None)
         self.not_labels = self.filter_json.get("org.matrix.not_labels", [])
 
-    def filters_all_types(self):
+    def filters_all_types(self) -> bool:
         return "*" in self.not_types
 
-    def filters_all_senders(self):
+    def filters_all_senders(self) -> bool:
         return "*" in self.not_senders
 
-    def filters_all_rooms(self):
+    def filters_all_rooms(self) -> bool:
         return "*" in self.not_rooms
 
-    def check(self, event):
+    def check(self, event: FilterEvent) -> bool:
         """Checks whether the filter matches the given event.
 
         Returns:
-            bool: True if the event matches
+            True if the event matches
         """
         # We usually get the full "events" as dictionaries coming through,
         # except for presence which actually gets passed around as its own
@@ -305,18 +329,25 @@ def check(self, event):
             room_id = event.get("room_id", None)
             ev_type = event.get("type", None)
 
-            content = event.get("content", {})
+            content = event.get("content") or {}
             # check if there is a string url field in the content for filtering purposes
             contains_url = isinstance(content.get("url"), str)
             labels = content.get(EventContentFields.LABELS, [])
 
         return self.check_fields(room_id, sender, ev_type, labels, contains_url)
 
-    def check_fields(self, room_id, sender, event_type, labels, contains_url):
+    def check_fields(
+        self,
+        room_id: Optional[str],
+        sender: Optional[str],
+        event_type: Optional[str],
+        labels: Container[str],
+        contains_url: bool,
+    ) -> bool:
         """Checks whether the filter matches the given event fields.
 
         Returns:
-            bool: True if the event fields match
+            True if the event fields match
         """
         literal_keys = {
             "rooms": lambda v: room_id == v,
@@ -343,14 +374,14 @@ def check_fields(self, room_id, sender, event_type, labels, contains_url):
 
         return True
 
-    def filter_rooms(self, room_ids):
+    def filter_rooms(self, room_ids: Iterable[str]) -> Set[str]:
         """Apply the 'rooms' filter to a given list of rooms.
 
         Args:
-            room_ids (list): A list of room_ids.
+            room_ids: A list of room_ids.
 
         Returns:
-            list: A list of room_ids that match the filter
+            A list of room_ids that match the filter
         """
         room_ids = set(room_ids)
 
@@ -363,23 +394,23 @@ def filter_rooms(self, room_ids):
 
         return room_ids
 
-    def filter(self, events):
+    def filter(self, events: Iterable[FilterEvent]) -> List[FilterEvent]:
         return list(filter(self.check, events))
 
-    def limit(self):
+    def limit(self) -> int:
         return self.filter_json.get("limit", 10)
 
-    def lazy_load_members(self):
+    def lazy_load_members(self) -> bool:
         return self.filter_json.get("lazy_load_members", False)
 
-    def include_redundant_members(self):
+    def include_redundant_members(self) -> bool:
         return self.filter_json.get("include_redundant_members", False)
 
-    def with_room_ids(self, room_ids):
+    def with_room_ids(self, room_ids: Iterable[str]) -> "Filter":
         """Returns a new filter with the given room IDs appended.
 
         Args:
-            room_ids (iterable[unicode]): The room_ids to add
+            room_ids: The room_ids to add
 
         Returns:
             filter: A new filter including the given rooms and the old
@@ -390,8 +421,8 @@ def with_room_ids(self, room_ids):
         return newFilter
 
 
-def _matches_wildcard(actual_value, filter_value):
-    if filter_value.endswith("*"):
+def _matches_wildcard(actual_value: Optional[str], filter_value: str) -> bool:
+    if filter_value.endswith("*") and isinstance(actual_value, str):
         type_prefix = filter_value[:-1]
         return actual_value.startswith(type_prefix)
     else:
diff --git a/synapse/api/ratelimiting.py b/synapse/api/ratelimiting.py
index cbdd74025..e8964097d 100644
--- a/synapse/api/ratelimiting.py
+++ b/synapse/api/ratelimiting.py
@@ -17,6 +17,7 @@
 from typing import Hashable, Optional, Tuple
 
 from synapse.api.errors import LimitExceededError
+from synapse.config.ratelimiting import RateLimitConfig
 from synapse.storage.databases.main import DataStore
 from synapse.types import Requester
 from synapse.util import Clock
@@ -233,3 +234,88 @@ async def ratelimit(
             raise LimitExceededError(
                 retry_after_ms=int(1000 * (time_allowed - time_now_s))
             )
+
+
+class RequestRatelimiter:
+    def __init__(
+        self,
+        store: DataStore,
+        clock: Clock,
+        rc_message: RateLimitConfig,
+        rc_admin_redaction: Optional[RateLimitConfig],
+    ):
+        self.store = store
+        self.clock = clock
+
+        # The rate_hz and burst_count are overridden on a per-user basis
+        self.request_ratelimiter = Ratelimiter(
+            store=self.store, clock=self.clock, rate_hz=0, burst_count=0
+        )
+        self._rc_message = rc_message
+
+        # Check whether ratelimiting room admin message redaction is enabled
+        # by the presence of rate limits in the config
+        if rc_admin_redaction:
+            self.admin_redaction_ratelimiter: Optional[Ratelimiter] = Ratelimiter(
+                store=self.store,
+                clock=self.clock,
+                rate_hz=rc_admin_redaction.per_second,
+                burst_count=rc_admin_redaction.burst_count,
+            )
+        else:
+            self.admin_redaction_ratelimiter = None
+
+    async def ratelimit(
+        self,
+        requester: Requester,
+        update: bool = True,
+        is_admin_redaction: bool = False,
+    ) -> None:
+        """Ratelimits requests.
+
+        Args:
+            requester
+            update: Whether to record that a request is being processed.
+                Set to False when doing multiple checks for one request (e.g.
+                to check up front if we would reject the request), and set to
+                True for the last call for a given request.
+            is_admin_redaction: Whether this is a room admin/moderator
+                redacting an event. If so then we may apply different
+                ratelimits depending on config.
+
+        Raises:
+            LimitExceededError if the request should be ratelimited
+        """
+        user_id = requester.user.to_string()
+
+        # The AS user itself is never rate limited.
+        app_service = self.store.get_app_service_by_user_id(user_id)
+        if app_service is not None:
+            return  # do not ratelimit app service senders
+
+        messages_per_second = self._rc_message.per_second
+        burst_count = self._rc_message.burst_count
+
+        # Check if there is a per user override in the DB.
+        override = await self.store.get_ratelimit_for_user(user_id)
+        if override:
+            # If overridden with a null Hz then ratelimiting has been entirely
+            # disabled for the user
+            if not override.messages_per_second:
+                return
+
+            messages_per_second = override.messages_per_second
+            burst_count = override.burst_count
+
+        if is_admin_redaction and self.admin_redaction_ratelimiter:
+            # If we have separate config for admin redactions, use a separate
+            # ratelimiter as to not have user_ids clash
+            await self.admin_redaction_ratelimiter.ratelimit(requester, update=update)
+        else:
+            # Override rate and burst count per-user
+            await self.request_ratelimiter.ratelimit(
+                requester,
+                rate_hz=messages_per_second,
+                burst_count=burst_count,
+                update=update,
+            )
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 548f6dcde..4a204a582 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -86,11 +86,11 @@ def start_worker_reactor(appname, config, run_command=reactor.run):
 
     start_reactor(
         appname,
-        soft_file_limit=config.soft_file_limit,
-        gc_thresholds=config.gc_thresholds,
+        soft_file_limit=config.server.soft_file_limit,
+        gc_thresholds=config.server.gc_thresholds,
         pid_file=config.worker.worker_pid_file,
         daemonize=config.worker.worker_daemonize,
-        print_pidfile=config.print_pidfile,
+        print_pidfile=config.server.print_pidfile,
         logger=logger,
         run_command=run_command,
     )
@@ -298,10 +298,10 @@ def refresh_certificate(hs):
     Refresh the TLS certificates that Synapse is using by re-reading them from
     disk and updating the TLS context factories to use them.
     """
-    if not hs.config.has_tls_listener():
+    if not hs.config.server.has_tls_listener():
         return
 
-    hs.config.read_certificate_from_disk()
+    hs.config.tls.read_certificate_from_disk()
     hs.tls_server_context_factory = context_factory.ServerContextFactory(hs.config)
 
     if hs._listening_services:
diff --git a/synapse/app/admin_cmd.py b/synapse/app/admin_cmd.py
index f2c5b7524..13d20af45 100644
--- a/synapse/app/admin_cmd.py
+++ b/synapse/app/admin_cmd.py
@@ -195,14 +195,14 @@ def start(config_options):
         config.logging.no_redirect_stdio = True
 
     # Explicitly disable background processes
-    config.update_user_directory = False
+    config.server.update_user_directory = False
     config.worker.run_background_tasks = False
-    config.start_pushers = False
+    config.worker.start_pushers = False
     config.pusher_shard_config.instances = []
-    config.send_federation = False
+    config.worker.send_federation = False
     config.federation_shard_config.instances = []
 
-    synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
+    synapse.events.USE_FROZEN_DICTS = config.server.use_frozen_dicts
 
     ss = AdminCmdServer(
         config.server.server_name,
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index 3036e1b4a..7489f31d9 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -462,7 +462,7 @@ def start(config_options):
         # For other worker types we force this to off.
         config.server.update_user_directory = False
 
-    synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
+    synapse.events.USE_FROZEN_DICTS = config.server.use_frozen_dicts
     synapse.util.caches.TRACK_MEMORY_USAGE = config.caches.track_memory_usage
 
     if config.server.gc_seconds:
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 205831dcd..422f03cc0 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -234,7 +234,7 @@ def _configure_named_resource(self, name, compress=False):
             )
 
         if name in ["media", "federation", "client"]:
-            if self.config.media.enable_media_repo:
+            if self.config.server.enable_media_repo:
                 media_repo = self.get_media_repository_resource()
                 resources.update(
                     {MEDIA_PREFIX: media_repo, LEGACY_MEDIA_PREFIX: media_repo}
@@ -248,7 +248,7 @@ def _configure_named_resource(self, name, compress=False):
             resources[SERVER_KEY_V2_PREFIX] = KeyApiV2Resource(self)
 
         if name == "webclient":
-            webclient_loc = self.config.web_client_location
+            webclient_loc = self.config.server.web_client_location
 
             if webclient_loc is None:
                 logger.warning(
@@ -343,7 +343,7 @@ def setup(config_options):
         # generating config files and shouldn't try to continue.
         sys.exit(0)
 
-    events.USE_FROZEN_DICTS = config.use_frozen_dicts
+    events.USE_FROZEN_DICTS = config.server.use_frozen_dicts
     synapse.util.caches.TRACK_MEMORY_USAGE = config.caches.track_memory_usage
 
     if config.server.gc_seconds:
@@ -439,11 +439,11 @@ def profiled(*args, **kargs):
 
     _base.start_reactor(
         "synapse-homeserver",
-        soft_file_limit=hs.config.soft_file_limit,
-        gc_thresholds=hs.config.gc_thresholds,
-        pid_file=hs.config.pid_file,
-        daemonize=hs.config.daemonize,
-        print_pidfile=hs.config.print_pidfile,
+        soft_file_limit=hs.config.server.soft_file_limit,
+        gc_thresholds=hs.config.server.gc_thresholds,
+        pid_file=hs.config.server.pid_file,
+        daemonize=hs.config.server.daemonize,
+        print_pidfile=hs.config.server.print_pidfile,
         logger=logger,
     )
 
diff --git a/synapse/app/phone_stats_home.py b/synapse/app/phone_stats_home.py
index 49e7a45e5..fcd01e833 100644
--- a/synapse/app/phone_stats_home.py
+++ b/synapse/app/phone_stats_home.py
@@ -74,7 +74,7 @@ async def phone_stats_home(hs, stats, stats_process=_stats_process):
     store = hs.get_datastore()
 
     stats["homeserver"] = hs.config.server.server_name
-    stats["server_context"] = hs.config.server_context
+    stats["server_context"] = hs.config.server.server_context
     stats["timestamp"] = now
     stats["uptime_seconds"] = uptime
     version = sys.version_info
@@ -171,7 +171,7 @@ async def generate_monthly_active_users():
         current_mau_count_by_service = {}
         reserved_users = ()
         store = hs.get_datastore()
-        if hs.config.limit_usage_by_mau or hs.config.mau_stats_only:
+        if hs.config.server.limit_usage_by_mau or hs.config.server.mau_stats_only:
             current_mau_count = await store.get_monthly_active_count()
             current_mau_count_by_service = (
                 await store.get_monthly_active_count_by_service()
@@ -183,9 +183,9 @@ async def generate_monthly_active_users():
             current_mau_by_service_gauge.labels(app_service).set(float(count))
 
         registered_reserved_users_mau_gauge.set(float(len(reserved_users)))
-        max_mau_gauge.set(float(hs.config.max_mau_value))
+        max_mau_gauge.set(float(hs.config.server.max_mau_value))
 
-    if hs.config.limit_usage_by_mau or hs.config.mau_stats_only:
+    if hs.config.server.limit_usage_by_mau or hs.config.server.mau_stats_only:
         generate_monthly_active_users()
         clock.looping_call(generate_monthly_active_users, 5 * 60 * 1000)
     # End of monthly active user settings
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index d974a1a2a..7c4428a13 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -118,21 +118,6 @@ def __init__(self, root_config=None):
             "synapse", "res/templates"
         )
 
-    def __getattr__(self, item: str) -> Any:
-        """
-        Try and fetch a configuration option that does not exist on this class.
-
-        This is so that existing configs that rely on `self.value`, where value
-        is actually from a different config section, continue to work.
-        """
-        if item in ["generate_config_section", "read_config"]:
-            raise AttributeError(item)
-
-        if self.root is None:
-            raise AttributeError(item)
-        else:
-            return self.root._get_unclassed_config(self.section, item)
-
     @staticmethod
     def parse_size(value):
         if isinstance(value, int):
@@ -289,7 +274,9 @@ def read_templates(
         env.filters.update(
             {
                 "format_ts": _format_ts_filter,
-                "mxc_to_http": _create_mxc_to_http_filter(self.public_baseurl),
+                "mxc_to_http": _create_mxc_to_http_filter(
+                    self.root.server.public_baseurl
+                ),
             }
         )
 
@@ -311,8 +298,6 @@ class RootConfig:
     config_classes = []
 
     def __init__(self):
-        self._configs = OrderedDict()
-
         for config_class in self.config_classes:
             if config_class.section is None:
                 raise ValueError("%r requires a section name" % (config_class,))
@@ -321,42 +306,7 @@ def __init__(self):
                 conf = config_class(self)
             except Exception as e:
                 raise Exception("Failed making %s: %r" % (config_class.section, e))
-            self._configs[config_class.section] = conf
-
-    def __getattr__(self, item: str) -> Any:
-        """
-        Redirect lookups on this object either to config objects, or values on
-        config objects, so that `config.tls.blah` works, as well as legacy uses
-        of things like `config.server_name`. It will first look up the config
-        section name, and then values on those config classes.
-        """
-        if item in self._configs.keys():
-            return self._configs[item]
-
-        return self._get_unclassed_config(None, item)
-
-    def _get_unclassed_config(self, asking_section: Optional[str], item: str):
-        """
-        Fetch a config value from one of the instantiated config classes that
-        has not been fetched directly.
-
-        Args:
-            asking_section: If this check is coming from a Config child, which
-                one? This section will not be asked if it has the value.
-            item: The configuration value key.
-
-        Raises:
-            AttributeError if no config classes have the config key. The body
-                will contain what sections were checked.
-        """
-        for key, val in self._configs.items():
-            if key == asking_section:
-                continue
-
-            if item in dir(val):
-                return getattr(val, item)
-
-        raise AttributeError(item, "not found in %s" % (list(self._configs.keys()),))
+            setattr(self, config_class.section, conf)
 
     def invoke_all(self, func_name: str, *args, **kwargs) -> MutableMapping[str, Any]:
         """
@@ -373,9 +323,11 @@ def invoke_all(self, func_name: str, *args, **kwargs) -> MutableMapping[str, Any
         """
         res = OrderedDict()
 
-        for name, config in self._configs.items():
+        for config_class in self.config_classes:
+            config = getattr(self, config_class.section)
+
             if hasattr(config, func_name):
-                res[name] = getattr(config, func_name)(*args, **kwargs)
+                res[config_class.section] = getattr(config, func_name)(*args, **kwargs)
 
         return res
 
diff --git a/synapse/config/account_validity.py b/synapse/config/account_validity.py
index ffaffc493..b56c2a24d 100644
--- a/synapse/config/account_validity.py
+++ b/synapse/config/account_validity.py
@@ -76,7 +76,7 @@ def read_config(self, config, **kwargs):
             )
 
         if self.account_validity_renew_by_email_enabled:
-            if not self.public_baseurl:
+            if not self.root.server.public_baseurl:
                 raise ConfigError("Can't send renewal emails without 'public_baseurl'")
 
         # Load account validity templates.
diff --git a/synapse/config/cas.py b/synapse/config/cas.py
index 901f4123e..9b58ecf3d 100644
--- a/synapse/config/cas.py
+++ b/synapse/config/cas.py
@@ -37,7 +37,7 @@ def read_config(self, config, **kwargs):
 
             # The public baseurl is required because it is used by the redirect
             # template.
-            public_baseurl = self.public_baseurl
+            public_baseurl = self.root.server.public_baseurl
             if not public_baseurl:
                 raise ConfigError("cas_config requires a public_baseurl to be set")
 
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index 936abe617..8ff59aa2f 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -19,7 +19,6 @@
 import logging
 import os
 from enum import Enum
-from typing import Optional
 
 import attr
 
@@ -135,7 +134,7 @@ def read_config(self, config, **kwargs):
             # msisdn is currently always remote while Synapse does not support any method of
             # sending SMS messages
             ThreepidBehaviour.REMOTE
-            if self.account_threepid_delegate_email
+            if self.root.registration.account_threepid_delegate_email
             else ThreepidBehaviour.LOCAL
         )
         # Prior to Synapse v1.4.0, there was another option that defined whether Synapse would
@@ -144,7 +143,7 @@ def read_config(self, config, **kwargs):
         # identity server in the process.
         self.using_identity_server_from_trusted_list = False
         if (
-            not self.account_threepid_delegate_email
+            not self.root.registration.account_threepid_delegate_email
             and config.get("trust_identity_server_for_password_resets", False) is True
         ):
             # Use the first entry in self.trusted_third_party_id_servers instead
@@ -156,7 +155,7 @@ def read_config(self, config, **kwargs):
 
                 # trusted_third_party_id_servers does not contain a scheme whereas
                 # account_threepid_delegate_email is expected to. Presume https
-                self.account_threepid_delegate_email: Optional[str] = (
+                self.root.registration.account_threepid_delegate_email = (
                     "https://" + first_trusted_identity_server
                 )
                 self.using_identity_server_from_trusted_list = True
@@ -335,7 +334,7 @@ def read_config(self, config, **kwargs):
                 "client_base_url", email_config.get("riot_base_url", None)
             )
 
-        if self.account_validity_renew_by_email_enabled:
+        if self.root.account_validity.account_validity_renew_by_email_enabled:
             expiry_template_html = email_config.get(
                 "expiry_template_html", "notice_expiry.html"
             )
diff --git a/synapse/config/key.py b/synapse/config/key.py
index 94a906304..015dbb8a6 100644
--- a/synapse/config/key.py
+++ b/synapse/config/key.py
@@ -145,11 +145,13 @@ def read_config(self, config, config_dir_path, **kwargs):
 
         # list of TrustedKeyServer objects
         self.key_servers = list(
-            _parse_key_servers(key_servers, self.federation_verify_certificates)
+            _parse_key_servers(
+                key_servers, self.root.tls.federation_verify_certificates
+            )
         )
 
         self.macaroon_secret_key = config.get(
-            "macaroon_secret_key", self.registration_shared_secret
+            "macaroon_secret_key", self.root.registration.registration_shared_secret
         )
 
         if not self.macaroon_secret_key:
diff --git a/synapse/config/oidc.py b/synapse/config/oidc.py
index 7e67fbada..10f579633 100644
--- a/synapse/config/oidc.py
+++ b/synapse/config/oidc.py
@@ -58,7 +58,7 @@ def read_config(self, config, **kwargs):
                     "Multiple OIDC providers have the idp_id %r." % idp_id
                 )
 
-        public_baseurl = self.public_baseurl
+        public_baseurl = self.root.server.public_baseurl
         if public_baseurl is None:
             raise ConfigError("oidc_config requires a public_baseurl to be set")
         self.oidc_callback_url = public_baseurl + "_synapse/client/oidc/callback"
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index 4353b1672..4ba1c544c 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -70,7 +70,10 @@ def read_config(self, config, **kwargs):
             raise ConfigError(
                 "account_threepid_delegates.msisdn must begin with http:// or https://"
             )
-        if self.account_threepid_delegate_msisdn and not self.public_baseurl:
+        if (
+            self.account_threepid_delegate_msisdn
+            and not self.root.server.public_baseurl
+        ):
             raise ConfigError(
                 "The configuration option `public_baseurl` is required if "
                 "`account_threepid_delegate.msisdn` is set, such that "
@@ -110,7 +113,7 @@ def read_config(self, config, **kwargs):
         if mxid_localpart:
             # Convert the localpart to a full mxid.
             self.auto_join_user_id = UserID(
-                mxid_localpart, self.server_name
+                mxid_localpart, self.root.server.server_name
             ).to_string()
 
         if self.autocreate_auto_join_rooms:
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 06a5cef76..0669eaefe 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -94,7 +94,7 @@ def read_config(self, config, **kwargs):
         # Only enable the media repo if either the media repo is enabled or the
         # current worker app is the media repo.
         if (
-            self.enable_media_repo is False
+            self.root.server.enable_media_repo is False
             and config.get("worker_app") != "synapse.app.media_repository"
         ):
             self.can_load_media_repo = False
diff --git a/synapse/config/saml2.py b/synapse/config/saml2.py
index 05e983625..9c51b6a25 100644
--- a/synapse/config/saml2.py
+++ b/synapse/config/saml2.py
@@ -199,7 +199,7 @@ def _default_saml_config_dict(
         """
         import saml2
 
-        public_baseurl = self.public_baseurl
+        public_baseurl = self.root.server.public_baseurl
         if public_baseurl is None:
             raise ConfigError("saml2_config requires a public_baseurl to be set")
 
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 65117b56b..68d8f8fd2 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -1,6 +1,4 @@
-# Copyright 2014-2016 OpenMarket Ltd
-# Copyright 2017-2018 New Vector Ltd
-# Copyright 2019 The Matrix.org Foundation C.I.C.
+# Copyright 2014-2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -19,7 +17,7 @@
 import os.path
 import re
 from textwrap import indent
-from typing import Any, Dict, Iterable, List, Optional, Set, Tuple
+from typing import Any, Dict, Iterable, List, Optional, Set, Tuple, Union
 
 import attr
 import yaml
@@ -184,49 +182,74 @@ def generate_ip_set(
 
 @attr.s(frozen=True)
 class HttpResourceConfig:
-    names = attr.ib(
-        type=List[str],
+    names: List[str] = attr.ib(
         factory=list,
         validator=attr.validators.deep_iterable(attr.validators.in_(KNOWN_RESOURCES)),  # type: ignore
     )
-    compress = attr.ib(
-        type=bool,
+    compress: bool = attr.ib(
         default=False,
         validator=attr.validators.optional(attr.validators.instance_of(bool)),  # type: ignore[arg-type]
     )
 
 
-@attr.s(frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class HttpListenerConfig:
     """Object describing the http-specific parts of the config of a listener"""
 
-    x_forwarded = attr.ib(type=bool, default=False)
-    resources = attr.ib(type=List[HttpResourceConfig], factory=list)
-    additional_resources = attr.ib(type=Dict[str, dict], factory=dict)
-    tag = attr.ib(type=str, default=None)
+    x_forwarded: bool = False
+    resources: List[HttpResourceConfig] = attr.ib(factory=list)
+    additional_resources: Dict[str, dict] = attr.ib(factory=dict)
+    tag: Optional[str] = None
 
 
-@attr.s(frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class ListenerConfig:
     """Object describing the configuration of a single listener."""
 
-    port = attr.ib(type=int, validator=attr.validators.instance_of(int))
-    bind_addresses = attr.ib(type=List[str])
-    type = attr.ib(type=str, validator=attr.validators.in_(KNOWN_LISTENER_TYPES))
-    tls = attr.ib(type=bool, default=False)
+    port: int = attr.ib(validator=attr.validators.instance_of(int))
+    bind_addresses: List[str]
+    type: str = attr.ib(validator=attr.validators.in_(KNOWN_LISTENER_TYPES))
+    tls: bool = False
 
     # http_options is only populated if type=http
-    http_options = attr.ib(type=Optional[HttpListenerConfig], default=None)
+    http_options: Optional[HttpListenerConfig] = None
 
 
-@attr.s(frozen=True)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class ManholeConfig:
     """Object describing the configuration of the manhole"""
 
-    username = attr.ib(type=str, validator=attr.validators.instance_of(str))
-    password = attr.ib(type=str, validator=attr.validators.instance_of(str))
-    priv_key = attr.ib(type=Optional[Key])
-    pub_key = attr.ib(type=Optional[Key])
+    username: str = attr.ib(validator=attr.validators.instance_of(str))
+    password: str = attr.ib(validator=attr.validators.instance_of(str))
+    priv_key: Optional[Key]
+    pub_key: Optional[Key]
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class RetentionConfig:
+    """Object describing the configuration of the manhole"""
+
+    interval: int
+    shortest_max_lifetime: Optional[int]
+    longest_max_lifetime: Optional[int]
+
+
+@attr.s(frozen=True)
+class LimitRemoteRoomsConfig:
+    enabled: bool = attr.ib(validator=attr.validators.instance_of(bool), default=False)
+    complexity: Union[float, int] = attr.ib(
+        validator=attr.validators.instance_of(
+            (float, int)  # type: ignore[arg-type] # noqa
+        ),
+        default=1.0,
+    )
+    complexity_error: str = attr.ib(
+        validator=attr.validators.instance_of(str),
+        default=ROOM_COMPLEXITY_TOO_GREAT,
+    )
+    admins_can_join: bool = attr.ib(
+        validator=attr.validators.instance_of(bool), default=False
+    )
 
 
 class ServerConfig(Config):
@@ -525,7 +548,7 @@ def read_config(self, config, **kwargs):
                 " greater than 'allowed_lifetime_max'"
             )
 
-        self.retention_purge_jobs: List[Dict[str, Optional[int]]] = []
+        self.retention_purge_jobs: List[RetentionConfig] = []
         for purge_job_config in retention_config.get("purge_jobs", []):
             interval_config = purge_job_config.get("interval")
 
@@ -559,20 +582,12 @@ def read_config(self, config, **kwargs):
                 )
 
             self.retention_purge_jobs.append(
-                {
-                    "interval": interval,
-                    "shortest_max_lifetime": shortest_max_lifetime,
-                    "longest_max_lifetime": longest_max_lifetime,
-                }
+                RetentionConfig(interval, shortest_max_lifetime, longest_max_lifetime)
             )
 
         if not self.retention_purge_jobs:
             self.retention_purge_jobs = [
-                {
-                    "interval": self.parse_duration("1d"),
-                    "shortest_max_lifetime": None,
-                    "longest_max_lifetime": None,
-                }
+                RetentionConfig(self.parse_duration("1d"), None, None)
             ]
 
         self.listeners = [parse_listener_def(x) for x in config.get("listeners", [])]
@@ -597,25 +612,6 @@ def read_config(self, config, **kwargs):
         self.gc_thresholds = read_gc_thresholds(config.get("gc_thresholds", None))
         self.gc_seconds = self.read_gc_intervals(config.get("gc_min_interval", None))
 
-        @attr.s
-        class LimitRemoteRoomsConfig:
-            enabled = attr.ib(
-                validator=attr.validators.instance_of(bool), default=False
-            )
-            complexity = attr.ib(
-                validator=attr.validators.instance_of(
-                    (float, int)  # type: ignore[arg-type] # noqa
-                ),
-                default=1.0,
-            )
-            complexity_error = attr.ib(
-                validator=attr.validators.instance_of(str),
-                default=ROOM_COMPLEXITY_TOO_GREAT,
-            )
-            admins_can_join = attr.ib(
-                validator=attr.validators.instance_of(bool), default=False
-            )
-
         self.limit_remote_rooms = LimitRemoteRoomsConfig(
             **(config.get("limit_remote_rooms") or {})
         )
diff --git a/synapse/config/server_notices.py b/synapse/config/server_notices.py
index 48bf3241b..bde4e879d 100644
--- a/synapse/config/server_notices.py
+++ b/synapse/config/server_notices.py
@@ -73,7 +73,9 @@ def read_config(self, config, **kwargs):
             return
 
         mxid_localpart = c["system_mxid_localpart"]
-        self.server_notices_mxid = UserID(mxid_localpart, self.server_name).to_string()
+        self.server_notices_mxid = UserID(
+            mxid_localpart, self.root.server.server_name
+        ).to_string()
         self.server_notices_mxid_display_name = c.get("system_mxid_display_name", None)
         self.server_notices_mxid_avatar_url = c.get("system_mxid_avatar_url", None)
         # todo: i18n
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index 524a7ff3a..11a9b76aa 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -103,8 +103,10 @@ def read_config(self, config, **kwargs):
         # the client's.
         # public_baseurl is an optional setting, so we only add the fallback's URL to the
         # list if it's provided (because we can't figure out what that URL is otherwise).
-        if self.public_baseurl:
-            login_fallback_url = self.public_baseurl + "_matrix/static/client/login"
+        if self.root.server.public_baseurl:
+            login_fallback_url = (
+                self.root.server.public_baseurl + "_matrix/static/client/login"
+            )
             self.sso_client_whitelist.append(login_fallback_url)
 
     def generate_config_section(self, **kwargs):
diff --git a/synapse/config/tls.py b/synapse/config/tls.py
index 5679f05e4..6227434ba 100644
--- a/synapse/config/tls.py
+++ b/synapse/config/tls.py
@@ -172,9 +172,12 @@ def is_disk_cert_valid(self, allow_self_signed=True):
                 )
 
         # YYYYMMDDhhmmssZ -- in UTC
-        expires_on = datetime.strptime(
-            tls_certificate.get_notAfter().decode("ascii"), "%Y%m%d%H%M%SZ"
-        )
+        expiry_data = tls_certificate.get_notAfter()
+        if expiry_data is None:
+            raise ValueError(
+                "TLS Certificate has no expiry date, and this is not permitted"
+            )
+        expires_on = datetime.strptime(expiry_data.decode("ascii"), "%Y%m%d%H%M%SZ")
         now = datetime.utcnow()
         days_remaining = (expires_on - now).days
         return days_remaining
diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index 650402836..ca0293a3d 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -41,42 +41,112 @@
 logger = logging.getLogger(__name__)
 
 
-def check(
-    room_version_obj: RoomVersion,
-    event: EventBase,
-    auth_events: StateMap[EventBase],
-    do_sig_check: bool = True,
-    do_size_check: bool = True,
+def validate_event_for_room_version(
+    room_version_obj: RoomVersion, event: EventBase
 ) -> None:
-    """Checks if this event is correctly authed.
+    """Ensure that the event complies with the limits, and has the right signatures
+
+    NB: does not *validate* the signatures - it assumes that any signatures present
+    have already been checked.
+
+    NB: it does not check that the event satisfies the auth rules (that is done in
+    check_auth_rules_for_event) - these tests are independent of the rest of the state
+    in the room.
+
+    NB: This is used to check events that have been received over federation. As such,
+    it can only enforce the checks specified in the relevant room version, to avoid
+    a split-brain situation where some servers accept such events, and others reject
+    them.
+
+    TODO: consider moving this into EventValidator
 
     Args:
-        room_version_obj: the version of the room
-        event: the event being checked.
-        auth_events: the existing room state.
-        do_sig_check: True if it should be verified that the sending server
-            signed the event.
-        do_size_check: True if the size of the event fields should be verified.
+        room_version_obj: the version of the room which contains this event
+        event: the event to be checked
 
     Raises:
-        AuthError if the checks fail
-
-    Returns:
-         if the auth checks pass.
+        SynapseError if there is a problem with the event
     """
-    assert isinstance(auth_events, dict)
-
-    if do_size_check:
-        _check_size_limits(event)
+    _check_size_limits(event)
 
     if not hasattr(event, "room_id"):
         raise AuthError(500, "Event has no room_id: %s" % event)
 
-    room_id = event.room_id
+    # check that the event has the correct signatures
+    sender_domain = get_domain_from_id(event.sender)
+
+    is_invite_via_3pid = (
+        event.type == EventTypes.Member
+        and event.membership == Membership.INVITE
+        and "third_party_invite" in event.content
+    )
+
+    # Check the sender's domain has signed the event
+    if not event.signatures.get(sender_domain):
+        # We allow invites via 3pid to have a sender from a different
+        # HS, as the sender must match the sender of the original
+        # 3pid invite. This is checked further down with the
+        # other dedicated membership checks.
+        if not is_invite_via_3pid:
+            raise AuthError(403, "Event not signed by sender's server")
+
+    if event.format_version in (EventFormatVersions.V1,):
+        # Only older room versions have event IDs to check.
+        event_id_domain = get_domain_from_id(event.event_id)
+
+        # Check the origin domain has signed the event
+        if not event.signatures.get(event_id_domain):
+            raise AuthError(403, "Event not signed by sending server")
+
+    is_invite_via_allow_rule = (
+        room_version_obj.msc3083_join_rules
+        and event.type == EventTypes.Member
+        and event.membership == Membership.JOIN
+        and EventContentFields.AUTHORISING_USER in event.content
+    )
+    if is_invite_via_allow_rule:
+        authoriser_domain = get_domain_from_id(
+            event.content[EventContentFields.AUTHORISING_USER]
+        )
+        if not event.signatures.get(authoriser_domain):
+            raise AuthError(403, "Event not signed by authorising server")
+
+
+def check_auth_rules_for_event(
+    room_version_obj: RoomVersion, event: EventBase, auth_events: StateMap[EventBase]
+) -> None:
+    """Check that an event complies with the auth rules
+
+    Checks whether an event passes the auth rules with a given set of state events
+
+    Assumes that we have already checked that the event is the right shape (it has
+    enough signatures, has a room ID, etc). In other words:
+
+     - it's fine for use in state resolution, when we have already decided whether to
+       accept the event or not, and are now trying to decide whether it should make it
+       into the room state
+
+     - when we're doing the initial event auth, it is only suitable in combination with
+       a bunch of other tests.
+
+    Args:
+        room_version_obj: the version of the room
+        event: the event being checked.
+        auth_events: the room state to check the events against.
+
+    Raises:
+        AuthError if the checks fail
+    """
+    assert isinstance(auth_events, dict)
 
     # We need to ensure that the auth events are actually for the same room, to
     # stop people from using powers they've been granted in other rooms for
     # example.
+    #
+    # Arguably we don't need to do this when we're just doing state res, as presumably
+    # the state res algorithm isn't silly enough to give us events from different rooms.
+    # Still, it's easier to do it anyway.
+    room_id = event.room_id
     for auth_event in auth_events.values():
         if auth_event.room_id != room_id:
             raise AuthError(
@@ -85,44 +155,12 @@ def check(
                 "which is in room %s"
                 % (event.event_id, room_id, auth_event.event_id, auth_event.room_id),
             )
-
-    if do_sig_check:
-        sender_domain = get_domain_from_id(event.sender)
-
-        is_invite_via_3pid = (
-            event.type == EventTypes.Member
-            and event.membership == Membership.INVITE
-            and "third_party_invite" in event.content
-        )
-
-        # Check the sender's domain has signed the event
-        if not event.signatures.get(sender_domain):
-            # We allow invites via 3pid to have a sender from a different
-            # HS, as the sender must match the sender of the original
-            # 3pid invite. This is checked further down with the
-            # other dedicated membership checks.
-            if not is_invite_via_3pid:
-                raise AuthError(403, "Event not signed by sender's server")
-
-        if event.format_version in (EventFormatVersions.V1,):
-            # Only older room versions have event IDs to check.
-            event_id_domain = get_domain_from_id(event.event_id)
-
-            # Check the origin domain has signed the event
-            if not event.signatures.get(event_id_domain):
-                raise AuthError(403, "Event not signed by sending server")
-
-        is_invite_via_allow_rule = (
-            event.type == EventTypes.Member
-            and event.membership == Membership.JOIN
-            and EventContentFields.AUTHORISING_USER in event.content
-        )
-        if is_invite_via_allow_rule:
-            authoriser_domain = get_domain_from_id(
-                event.content[EventContentFields.AUTHORISING_USER]
+        if auth_event.rejected_reason:
+            raise AuthError(
+                403,
+                "During auth for event %s: found rejected event %s in the state"
+                % (event.event_id, auth_event.event_id),
             )
-            if not event.signatures.get(authoriser_domain):
-                raise AuthError(403, "Event not signed by authorising server")
 
     # Implementation of https://matrix.org/docs/spec/rooms/v1#authorization-rules
     #
diff --git a/synapse/events/builder.py b/synapse/events/builder.py
index 87e2bb123..50f2a4c1f 100644
--- a/synapse/events/builder.py
+++ b/synapse/events/builder.py
@@ -18,10 +18,8 @@
 from nacl.signing import SigningKey
 
 from synapse.api.constants import MAX_DEPTH
-from synapse.api.errors import UnsupportedRoomVersionError
 from synapse.api.room_versions import (
     KNOWN_EVENT_FORMAT_VERSIONS,
-    KNOWN_ROOM_VERSIONS,
     EventFormatVersions,
     RoomVersion,
 )
@@ -197,24 +195,6 @@ def __init__(self, hs: "HomeServer"):
         self.state = hs.get_state_handler()
         self._event_auth_handler = hs.get_event_auth_handler()
 
-    def new(self, room_version: str, key_values: dict) -> EventBuilder:
-        """Generate an event builder appropriate for the given room version
-
-        Deprecated: use for_room_version with a RoomVersion object instead
-
-        Args:
-            room_version: Version of the room that we're creating an event builder for
-            key_values: Fields used as the basis of the new event
-
-        Returns:
-            EventBuilder
-        """
-        v = KNOWN_ROOM_VERSIONS.get(room_version)
-        if not v:
-            # this can happen if support is withdrawn for a room version
-            raise UnsupportedRoomVersionError()
-        return self.for_room_version(v, key_values)
-
     def for_room_version(
         self, room_version: RoomVersion, key_values: dict
     ) -> EventBuilder:
diff --git a/synapse/events/presence_router.py b/synapse/events/presence_router.py
index eb4556cdc..68b8b1902 100644
--- a/synapse/events/presence_router.py
+++ b/synapse/events/presence_router.py
@@ -45,11 +45,11 @@ def load_legacy_presence_router(hs: "HomeServer"):
     configuration, and registers the hooks they implement.
     """
 
-    if hs.config.presence_router_module_class is None:
+    if hs.config.server.presence_router_module_class is None:
         return
 
-    module = hs.config.presence_router_module_class
-    config = hs.config.presence_router_config
+    module = hs.config.server.presence_router_module_class
+    config = hs.config.server.presence_router_config
     api = hs.get_module_api()
 
     presence_router = module(config=config, module_api=api)
diff --git a/synapse/events/spamcheck.py b/synapse/events/spamcheck.py
index 3134beb8d..666d28b77 100644
--- a/synapse/events/spamcheck.py
+++ b/synapse/events/spamcheck.py
@@ -276,9 +276,7 @@ async def check_event_for_spam(
 
         return False
 
-    async def user_may_join_room(
-        self, user_id: str, room_id: str, is_invited: bool
-    ) -> bool:
+    async def user_may_join_room(self, user_id: str, room_id: str, is_invited: bool):
         """Checks if a given users is allowed to join a room.
         Not called when a user creates a room.
 
@@ -288,7 +286,7 @@ async def user_may_join_room(
             is_invited: Whether the user is invited into the room
 
         Returns:
-            Whether the user may join the room
+            bool: Whether the user may join the room
         """
         for callback in self._user_may_join_room_callbacks:
             if await callback(user_id, room_id, is_invited) is False:
diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py
index d94b1bb4d..976d9fa44 100644
--- a/synapse/events/third_party_rules.py
+++ b/synapse/events/third_party_rules.py
@@ -217,6 +217,15 @@ async def check_event_allowed(
         for callback in self._check_event_allowed_callbacks:
             try:
                 res, replacement_data = await callback(event, state_events)
+            except SynapseError as e:
+                # FIXME: Being able to throw SynapseErrors is relied upon by
+                # some modules. PR #10386 accidentally broke this ability.
+                # That said, we aren't keen on exposing this implementation detail
+                # to modules and we should one day have a proper way to do what
+                # is wanted.
+                # This module callback needs a rework so that hacks such as
+                # this one are not necessary.
+                raise e
             except Exception as e:
                 logger.warning("Failed to run module API callback %s: %s", callback, e)
                 continue
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 38fccd1ef..520edbbf6 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -372,7 +372,7 @@ class EventClientSerializer:
     def __init__(self, hs):
         self.store = hs.get_datastore()
         self.experimental_msc1849_support_enabled = (
-            hs.config.experimental_msc1849_support_enabled
+            hs.config.server.experimental_msc1849_support_enabled
         )
 
     async def serialize_event(
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 5f4383eeb..d8c0b86f2 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -1008,7 +1008,10 @@ async def _process_incoming_pdus_in_room_inner(
             async with lock:
                 logger.info("handling received PDU: %s", event)
                 try:
-                    await self._federation_event_handler.on_receive_pdu(origin, event)
+                    with nested_logging_context(event.event_id):
+                        await self._federation_event_handler.on_receive_pdu(
+                            origin, event
+                        )
                 except FederationError as e:
                     # XXX: Ideally we'd inform the remote we failed to process
                     # the event, but we can't return an error in the transaction
diff --git a/synapse/federation/transport/server/__init__.py b/synapse/federation/transport/server/__init__.py
index 95176ba6f..c32539bf5 100644
--- a/synapse/federation/transport/server/__init__.py
+++ b/synapse/federation/transport/server/__init__.py
@@ -117,7 +117,7 @@ def __init__(
     ):
         super().__init__(hs, authenticator, ratelimiter, server_name)
         self.handler = hs.get_room_list_handler()
-        self.allow_access = hs.config.allow_public_rooms_over_federation
+        self.allow_access = hs.config.server.allow_public_rooms_over_federation
 
     async def on_GET(
         self, origin: str, content: Literal[None], query: Dict[bytes, List[bytes]]
diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
deleted file mode 100644
index 0ccef884e..000000000
--- a/synapse/handlers/_base.py
+++ /dev/null
@@ -1,120 +0,0 @@
-# Copyright 2014 - 2016 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import logging
-from typing import TYPE_CHECKING, Optional
-
-from synapse.api.ratelimiting import Ratelimiter
-from synapse.types import Requester
-
-if TYPE_CHECKING:
-    from synapse.server import HomeServer
-
-logger = logging.getLogger(__name__)
-
-
-class BaseHandler:
-    """
-    Common base class for the event handlers.
-
-    Deprecated: new code should not use this. Instead, Handler classes should define the
-    fields they actually need. The utility methods should either be factored out to
-    standalone helper functions, or to different Handler classes.
-    """
-
-    def __init__(self, hs: "HomeServer"):
-        self.store = hs.get_datastore()
-        self.auth = hs.get_auth()
-        self.notifier = hs.get_notifier()
-        self.state_handler = hs.get_state_handler()
-        self.distributor = hs.get_distributor()
-        self.clock = hs.get_clock()
-        self.hs = hs
-
-        # The rate_hz and burst_count are overridden on a per-user basis
-        self.request_ratelimiter = Ratelimiter(
-            store=self.store, clock=self.clock, rate_hz=0, burst_count=0
-        )
-        self._rc_message = self.hs.config.ratelimiting.rc_message
-
-        # Check whether ratelimiting room admin message redaction is enabled
-        # by the presence of rate limits in the config
-        if self.hs.config.ratelimiting.rc_admin_redaction:
-            self.admin_redaction_ratelimiter: Optional[Ratelimiter] = Ratelimiter(
-                store=self.store,
-                clock=self.clock,
-                rate_hz=self.hs.config.ratelimiting.rc_admin_redaction.per_second,
-                burst_count=self.hs.config.ratelimiting.rc_admin_redaction.burst_count,
-            )
-        else:
-            self.admin_redaction_ratelimiter = None
-
-        self.server_name = hs.hostname
-
-        self.event_builder_factory = hs.get_event_builder_factory()
-
-    async def ratelimit(
-        self,
-        requester: Requester,
-        update: bool = True,
-        is_admin_redaction: bool = False,
-    ) -> None:
-        """Ratelimits requests.
-
-        Args:
-            requester
-            update: Whether to record that a request is being processed.
-                Set to False when doing multiple checks for one request (e.g.
-                to check up front if we would reject the request), and set to
-                True for the last call for a given request.
-            is_admin_redaction: Whether this is a room admin/moderator
-                redacting an event. If so then we may apply different
-                ratelimits depending on config.
-
-        Raises:
-            LimitExceededError if the request should be ratelimited
-        """
-        user_id = requester.user.to_string()
-
-        # The AS user itself is never rate limited.
-        app_service = self.store.get_app_service_by_user_id(user_id)
-        if app_service is not None:
-            return  # do not ratelimit app service senders
-
-        messages_per_second = self._rc_message.per_second
-        burst_count = self._rc_message.burst_count
-
-        # Check if there is a per user override in the DB.
-        override = await self.store.get_ratelimit_for_user(user_id)
-        if override:
-            # If overridden with a null Hz then ratelimiting has been entirely
-            # disabled for the user
-            if not override.messages_per_second:
-                return
-
-            messages_per_second = override.messages_per_second
-            burst_count = override.burst_count
-
-        if is_admin_redaction and self.admin_redaction_ratelimiter:
-            # If we have separate config for admin redactions, use a separate
-            # ratelimiter as to not have user_ids clash
-            await self.admin_redaction_ratelimiter.ratelimit(requester, update=update)
-        else:
-            # Override rate and burst count per-user
-            await self.request_ratelimiter.ratelimit(
-                requester,
-                rate_hz=messages_per_second,
-                burst_count=burst_count,
-                update=update,
-            )
diff --git a/synapse/handlers/account_validity.py b/synapse/handlers/account_validity.py
index d0a42e9a8..4a4cf8e7b 100644
--- a/synapse/handlers/account_validity.py
+++ b/synapse/handlers/account_validity.py
@@ -59,7 +59,9 @@ def __init__(self, hs: "HomeServer"):
             hs.config.account_validity.account_validity_renew_by_email_enabled
         )
 
-        self._show_users_in_user_directory = self.hs.config.show_users_in_user_directory
+        self._show_users_in_user_directory = (
+            self.hs.config.server.show_users_in_user_directory
+        )
 
         self._account_validity_period = None
         if self._account_validity_enabled:
@@ -72,12 +74,8 @@ def __init__(self, hs: "HomeServer"):
             and self._account_validity_renew_by_email_enabled
         ):
             # Don't do email-specific configuration if renewal by email is disabled.
-            self._template_html = (
-                hs.config.account_validity.account_validity_template_html
-            )
-            self._template_text = (
-                hs.config.account_validity.account_validity_template_text
-            )
+            self._template_html = hs.config.email.account_validity_template_html
+            self._template_text = hs.config.email.account_validity_template_text
             self._renew_email_subject = (
                 hs.config.account_validity.account_validity_renew_email_subject
             )
diff --git a/synapse/handlers/admin.py b/synapse/handlers/admin.py
index bfa7f2c54..a53cd62d3 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -21,18 +21,15 @@
 from synapse.types import JsonDict, RoomStreamToken, StateMap, UserID
 from synapse.visibility import filter_events_for_client
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class AdminHandler(BaseHandler):
+class AdminHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.store = hs.get_datastore()
         self.storage = hs.get_storage()
         self.state_store = self.storage.state
 
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index a8c717efd..f4612a5b9 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -52,7 +52,6 @@
     UserDeactivatedError,
 )
 from synapse.api.ratelimiting import Ratelimiter
-from synapse.handlers._base import BaseHandler
 from synapse.handlers.ui_auth import (
     INTERACTIVE_AUTH_CHECKERS,
     UIAuthSessionDataConstants,
@@ -186,19 +185,20 @@ class LoginTokenAttributes:
     auth_provider_id = attr.ib(type=str)
 
 
-class AuthHandler(BaseHandler):
+class AuthHandler:
     SESSION_EXPIRE_MS = 48 * 60 * 60 * 1000
 
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
         self.checkers: Dict[str, UserInteractiveAuthChecker] = {}
         for auth_checker_class in INTERACTIVE_AUTH_CHECKERS:
             inst = auth_checker_class(hs)
             if inst.is_enabled():
                 self.checkers[inst.AUTH_TYPE] = inst  # type: ignore
 
-        self.bcrypt_rounds = hs.config.bcrypt_rounds
+        self.bcrypt_rounds = hs.config.registration.bcrypt_rounds
 
         # we can't use hs.get_module_api() here, because to do so will create an
         # import loop.
diff --git a/synapse/handlers/deactivate_account.py b/synapse/handlers/deactivate_account.py
index 98da9bbba..510c366e8 100644
--- a/synapse/handlers/deactivate_account.py
+++ b/synapse/handlers/deactivate_account.py
@@ -19,19 +19,17 @@
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.types import Requester, UserID, create_requester
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class DeactivateAccountHandler(BaseHandler):
+class DeactivateAccountHandler:
     """Handler which deals with deactivating user accounts."""
 
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
         self.hs = hs
         self._auth_handler = hs.get_auth_handler()
         self._device_handler = hs.get_device_handler()
@@ -138,6 +136,10 @@ async def deactivate_account(
         # delete from user directory
         await self.user_directory_handler.handle_local_user_deactivated(user_id)
 
+        # If the user is present in the monthly active users table
+        # remove them
+        await self.store.remove_deactivated_user_from_mau_table(user_id)
+
         # Mark the user as erased, if they asked for that
         if erase_data:
             user = UserID.from_string(user_id)
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index 35334725d..75e601976 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -40,8 +40,6 @@
 from synapse.util.metrics import measure_func
 from synapse.util.retryutils import NotRetryingDestination
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -50,14 +48,16 @@
 MAX_DEVICE_DISPLAY_NAME_LEN = 100
 
 
-class DeviceWorkerHandler(BaseHandler):
+class DeviceWorkerHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.clock = hs.get_clock()
         self.hs = hs
+        self.store = hs.get_datastore()
+        self.notifier = hs.get_notifier()
         self.state = hs.get_state_handler()
         self.state_store = hs.get_storage().state
         self._auth_handler = hs.get_auth_handler()
+        self.server_name = hs.hostname
 
     @trace
     async def get_devices_by_user(self, user_id: str) -> List[JsonDict]:
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index 5cfba3c81..14ed7d987 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -31,26 +31,25 @@
 from synapse.storage.databases.main.directory import RoomAliasMapping
 from synapse.types import JsonDict, Requester, RoomAlias, UserID, get_domain_from_id
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class DirectoryHandler(BaseHandler):
+class DirectoryHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.auth = hs.get_auth()
+        self.hs = hs
         self.state = hs.get_state_handler()
         self.appservice_handler = hs.get_application_service_handler()
         self.event_creation_handler = hs.get_event_creation_handler()
         self.store = hs.get_datastore()
         self.config = hs.config
         self.enable_room_list_search = hs.config.roomdirectory.enable_room_list_search
-        self.require_membership = hs.config.require_membership_for_aliases
+        self.require_membership = hs.config.server.require_membership_for_aliases
         self.third_party_event_rules = hs.get_third_party_event_rules()
+        self.server_name = hs.hostname
 
         self.federation = hs.get_federation_client()
         hs.get_federation_registry().register_query_handler(
diff --git a/synapse/handlers/event_auth.py b/synapse/handlers/event_auth.py
index cb81fa098..d089c5628 100644
--- a/synapse/handlers/event_auth.py
+++ b/synapse/handlers/event_auth.py
@@ -22,7 +22,8 @@
     RestrictedJoinRuleTypes,
 )
 from synapse.api.errors import AuthError, Codes, SynapseError
-from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
+from synapse.api.room_versions import RoomVersion
+from synapse.event_auth import check_auth_rules_for_event
 from synapse.events import EventBase
 from synapse.events.builder import EventBuilder
 from synapse.events.snapshot import EventContext
@@ -45,21 +46,17 @@ def __init__(self, hs: "HomeServer"):
         self._store = hs.get_datastore()
         self._server_name = hs.hostname
 
-    async def check_from_context(
+    async def check_auth_rules_from_context(
         self,
-        room_version: str,
+        room_version_obj: RoomVersion,
         event: EventBase,
         context: EventContext,
-        do_sig_check: bool = True,
     ) -> None:
+        """Check an event passes the auth rules at its own auth events"""
         auth_event_ids = event.auth_event_ids()
         auth_events_by_id = await self._store.get_events(auth_event_ids)
         auth_events = {(e.type, e.state_key): e for e in auth_events_by_id.values()}
-
-        room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
-        event_auth.check(
-            room_version_obj, event, auth_events=auth_events, do_sig_check=do_sig_check
-        )
+        check_auth_rules_for_event(room_version_obj, event, auth_events)
 
     def compute_auth_events(
         self,
diff --git a/synapse/handlers/events.py b/synapse/handlers/events.py
index 4b3f03707..1f64534a8 100644
--- a/synapse/handlers/events.py
+++ b/synapse/handlers/events.py
@@ -25,8 +25,6 @@
 from synapse.types import JsonDict, UserID
 from synapse.visibility import filter_events_for_client
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -34,11 +32,11 @@
 logger = logging.getLogger(__name__)
 
 
-class EventStreamHandler(BaseHandler):
+class EventStreamHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.store = hs.get_datastore()
         self.clock = hs.get_clock()
+        self.hs = hs
 
         self.notifier = hs.get_notifier()
         self.state = hs.get_state_handler()
@@ -138,9 +136,9 @@ async def get_stream(
             return chunk
 
 
-class EventHandler(BaseHandler):
+class EventHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
         self.storage = hs.get_storage()
 
     async def get_event(
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index adbd150e4..3e341bd28 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -45,11 +45,14 @@
 )
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion, RoomVersions
 from synapse.crypto.event_signing import compute_event_signature
+from synapse.event_auth import (
+    check_auth_rules_for_event,
+    validate_event_for_room_version,
+)
 from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.events.validator import EventValidator
 from synapse.federation.federation_client import InvalidResponseError
-from synapse.handlers._base import BaseHandler
 from synapse.http.servlet import assert_params_in_dict
 from synapse.logging.context import (
     make_deferred_yieldable,
@@ -74,15 +77,13 @@
 logger = logging.getLogger(__name__)
 
 
-class FederationHandler(BaseHandler):
+class FederationHandler:
     """Handles general incoming federation requests
 
     Incoming events are *not* handled here, for which see FederationEventHandler.
     """
 
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
         self.hs = hs
 
         self.store = hs.get_datastore()
@@ -95,6 +96,7 @@ def __init__(self, hs: "HomeServer"):
         self.is_mine_id = hs.is_mine_id
         self.spam_checker = hs.get_spam_checker()
         self.event_creation_handler = hs.get_event_creation_handler()
+        self.event_builder_factory = hs.get_event_builder_factory()
         self._event_auth_handler = hs.get_event_auth_handler()
         self._server_notices_mxid = hs.config.servernotices.server_notices_mxid
         self.config = hs.config
@@ -723,8 +725,8 @@ async def on_make_join_request(
                         state_ids,
                     )
 
-        builder = self.event_builder_factory.new(
-            room_version.identifier,
+        builder = self.event_builder_factory.for_room_version(
+            room_version,
             {
                 "type": EventTypes.Member,
                 "content": event_content,
@@ -747,10 +749,9 @@ async def on_make_join_request(
 
         # The remote hasn't signed it yet, obviously. We'll do the full checks
         # when we get the event back in `on_send_join_request`
-        await self._event_auth_handler.check_from_context(
-            room_version.identifier, event, context, do_sig_check=False
+        await self._event_auth_handler.check_auth_rules_from_context(
+            room_version, event, context
         )
-
         return event
 
     async def on_invite_request(
@@ -767,7 +768,7 @@ async def on_invite_request(
         if is_blocked:
             raise SynapseError(403, "This room has been blocked on this server")
 
-        if self.hs.config.block_non_admin_invites:
+        if self.hs.config.server.block_non_admin_invites:
             raise SynapseError(403, "This server does not accept room invites")
 
         if not await self.spam_checker.user_may_invite(
@@ -902,9 +903,9 @@ async def on_make_leave_request(
             )
             raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
 
-        room_version = await self.store.get_room_version_id(room_id)
-        builder = self.event_builder_factory.new(
-            room_version,
+        room_version_obj = await self.store.get_room_version(room_id)
+        builder = self.event_builder_factory.for_room_version(
+            room_version_obj,
             {
                 "type": EventTypes.Member,
                 "content": {"membership": Membership.LEAVE},
@@ -921,8 +922,8 @@ async def on_make_leave_request(
         try:
             # The remote hasn't signed it yet, obviously. We'll do the full checks
             # when we get the event back in `on_send_leave_request`
-            await self._event_auth_handler.check_from_context(
-                room_version, event, context, do_sig_check=False
+            await self._event_auth_handler.check_auth_rules_from_context(
+                room_version_obj, event, context
             )
         except AuthError as e:
             logger.warning("Failed to create new leave %r because %s", event, e)
@@ -954,10 +955,10 @@ async def on_make_knock_request(
             )
             raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
 
-        room_version = await self.store.get_room_version_id(room_id)
+        room_version_obj = await self.store.get_room_version(room_id)
 
-        builder = self.event_builder_factory.new(
-            room_version,
+        builder = self.event_builder_factory.for_room_version(
+            room_version_obj,
             {
                 "type": EventTypes.Member,
                 "content": {"membership": Membership.KNOCK},
@@ -983,8 +984,8 @@ async def on_make_knock_request(
         try:
             # The remote hasn't signed it yet, obviously. We'll do the full checks
             # when we get the event back in `on_send_knock_request`
-            await self._event_auth_handler.check_from_context(
-                room_version, event, context, do_sig_check=False
+            await self._event_auth_handler.check_auth_rules_from_context(
+                room_version_obj, event, context
             )
         except AuthError as e:
             logger.warning("Failed to create new knock %r because %s", event, e)
@@ -1173,7 +1174,8 @@ async def _persist_auth_tree(
                 auth_for_e[(EventTypes.Create, "")] = create_event
 
             try:
-                event_auth.check(room_version, e, auth_events=auth_for_e)
+                validate_event_for_room_version(room_version, e)
+                check_auth_rules_for_event(room_version, e, auth_for_e)
             except SynapseError as err:
                 # we may get SynapseErrors here as well as AuthErrors. For
                 # instance, there are a couple of (ancient) events in some
@@ -1250,8 +1252,10 @@ async def exchange_third_party_invite(
         }
 
         if await self._event_auth_handler.check_host_in_room(room_id, self.hs.hostname):
-            room_version = await self.store.get_room_version_id(room_id)
-            builder = self.event_builder_factory.new(room_version, event_dict)
+            room_version_obj = await self.store.get_room_version(room_id)
+            builder = self.event_builder_factory.for_room_version(
+                room_version_obj, event_dict
+            )
 
             EventValidator().validate_builder(builder)
             event, context = await self.event_creation_handler.create_new_client_event(
@@ -1259,7 +1263,7 @@ async def exchange_third_party_invite(
             )
 
             event, context = await self.add_display_name_to_third_party_invite(
-                room_version, event_dict, event, context
+                room_version_obj, event_dict, event, context
             )
 
             EventValidator().validate_new(event, self.config)
@@ -1269,8 +1273,9 @@ async def exchange_third_party_invite(
             event.internal_metadata.send_on_behalf_of = self.hs.hostname
 
             try:
-                await self._event_auth_handler.check_from_context(
-                    room_version, event, context
+                validate_event_for_room_version(room_version_obj, event)
+                await self._event_auth_handler.check_auth_rules_from_context(
+                    room_version_obj, event, context
                 )
             except AuthError as e:
                 logger.warning("Denying new third party invite %r because %s", event, e)
@@ -1304,22 +1309,25 @@ async def on_exchange_third_party_invite_request(
 
         """
         assert_params_in_dict(event_dict, ["room_id"])
-        room_version = await self.store.get_room_version_id(event_dict["room_id"])
+        room_version_obj = await self.store.get_room_version(event_dict["room_id"])
 
         # NB: event_dict has a particular specced format we might need to fudge
         # if we change event formats too much.
-        builder = self.event_builder_factory.new(room_version, event_dict)
+        builder = self.event_builder_factory.for_room_version(
+            room_version_obj, event_dict
+        )
 
         event, context = await self.event_creation_handler.create_new_client_event(
             builder=builder
         )
         event, context = await self.add_display_name_to_third_party_invite(
-            room_version, event_dict, event, context
+            room_version_obj, event_dict, event, context
         )
 
         try:
-            await self._event_auth_handler.check_from_context(
-                room_version, event, context
+            validate_event_for_room_version(room_version_obj, event)
+            await self._event_auth_handler.check_auth_rules_from_context(
+                room_version_obj, event, context
             )
         except AuthError as e:
             logger.warning("Denying third party invite %r because %s", event, e)
@@ -1336,7 +1344,7 @@ async def on_exchange_third_party_invite_request(
 
     async def add_display_name_to_third_party_invite(
         self,
-        room_version: str,
+        room_version_obj: RoomVersion,
         event_dict: JsonDict,
         event: EventBase,
         context: EventContext,
@@ -1368,7 +1376,9 @@ async def add_display_name_to_third_party_invite(
             # auth checks. If we need the invite and don't have it then the
             # auth check code will explode appropriately.
 
-        builder = self.event_builder_factory.new(room_version, event_dict)
+        builder = self.event_builder_factory.for_room_version(
+            room_version_obj, event_dict
+        )
         EventValidator().validate_builder(builder)
         event, context = await self.event_creation_handler.create_new_client_event(
             builder=builder
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index 01fd84112..f640b417b 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -29,7 +29,6 @@
 
 from prometheus_client import Counter
 
-from synapse import event_auth
 from synapse.api.constants import (
     EventContentFields,
     EventTypes,
@@ -47,7 +46,11 @@
     SynapseError,
 )
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
-from synapse.event_auth import auth_types_for_event
+from synapse.event_auth import (
+    auth_types_for_event,
+    check_auth_rules_for_event,
+    validate_event_for_room_version,
+)
 from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.federation.federation_client import InvalidResponseError
@@ -68,11 +71,7 @@
     UserID,
     get_domain_from_id,
 )
-from synapse.util.async_helpers import (
-    Linearizer,
-    concurrently_execute,
-    yieldable_gather_results,
-)
+from synapse.util.async_helpers import Linearizer, concurrently_execute
 from synapse.util.iterutils import batch_iter
 from synapse.util.retryutils import NotRetryingDestination
 from synapse.util.stringutils import shortstr
@@ -357,6 +356,11 @@ async def on_send_membership_event(
                 )
 
         # all looks good, we can persist the event.
+
+        # First, precalculate the joined hosts so that the federation sender doesn't
+        # need to.
+        await self._event_creation_handler.cache_joined_hosts_for_event(event, context)
+
         await self._run_push_actions_and_persist_event(event, context)
         return event, context
 
@@ -890,6 +894,9 @@ async def _process_received_pdu(
                 backfilled=backfilled,
             )
         except AuthError as e:
+            # FIXME richvdh 2021/10/07 I don't think this is reachable. Let's log it
+            #   for now
+            logger.exception("Unexpected AuthError from _check_event_auth")
             raise FederationError("ERROR", e.code, e.msg, affected=event.event_id)
 
         await self._run_push_actions_and_persist_event(event, context, backfilled)
@@ -1011,9 +1018,8 @@ async def _handle_marker_event(self, origin: str, marker_event: EventBase) -> No
         room_version = await self._store.get_room_version(marker_event.room_id)
         create_event = await self._store.get_create_event_for_room(marker_event.room_id)
         room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR)
-        if (
-            not room_version.msc2716_historical
-            or not self._config.experimental.msc2716_enabled
+        if not room_version.msc2716_historical and (
+            not self._config.experimental.msc2716_enabled
             or marker_event.sender != room_creator
         ):
             return
@@ -1155,7 +1161,10 @@ async def _auth_and_persist_fetched_events(
                 return
 
             logger.info(
-                "Persisting %i of %i remaining events", len(roots), len(event_map)
+                "Persisting %i of %i remaining outliers: %s",
+                len(roots),
+                len(event_map),
+                shortstr(e.event_id for e in roots),
             )
 
             await self._auth_and_persist_fetched_events_inner(origin, room_id, roots)
@@ -1189,7 +1198,10 @@ async def _auth_and_persist_fetched_events_inner(
             allow_rejected=True,
         )
 
-        async def prep(event: EventBase) -> Optional[Tuple[EventBase, EventContext]]:
+        room_version = await self._store.get_room_version_id(room_id)
+        room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
+
+        def prep(event: EventBase) -> Optional[Tuple[EventBase, EventContext]]:
             with nested_logging_context(suffix=event.event_id):
                 auth = {}
                 for auth_event_id in event.auth_event_ids():
@@ -1207,17 +1219,16 @@ async def prep(event: EventBase) -> Optional[Tuple[EventBase, EventContext]]:
                     auth[(ae.type, ae.state_key)] = ae
 
                 context = EventContext.for_outlier()
-                context = await self._check_event_auth(
-                    origin,
-                    event,
-                    context,
-                    claimed_auth_event_map=auth,
-                )
+                try:
+                    validate_event_for_room_version(room_version_obj, event)
+                    check_auth_rules_for_event(room_version_obj, event, auth)
+                except AuthError as e:
+                    logger.warning("Rejecting %r because %s", event, e)
+                    context.rejected = RejectedReason.AUTH_ERROR
+
             return event, context
 
-        events_to_persist = (
-            x for x in await yieldable_gather_results(prep, fetched_events) if x
-        )
+        events_to_persist = (x for x in (prep(event) for event in fetched_events) if x)
         await self.persist_events_and_notify(room_id, tuple(events_to_persist))
 
     async def _check_event_auth(
@@ -1226,7 +1237,6 @@ async def _check_event_auth(
         event: EventBase,
         context: EventContext,
         state: Optional[Iterable[EventBase]] = None,
-        claimed_auth_event_map: Optional[StateMap[EventBase]] = None,
         backfilled: bool = False,
     ) -> EventContext:
         """
@@ -1242,42 +1252,45 @@ async def _check_event_auth(
                 The state events used to check the event for soft-fail. If this is
                 not provided the current state events will be used.
 
-            claimed_auth_event_map:
-                A map of (type, state_key) => event for the event's claimed auth_events.
-                Possibly including events that were rejected, or are in the wrong room.
-
-                Only populated when populating outliers.
-
             backfilled: True if the event was backfilled.
 
         Returns:
             The updated context object.
         """
-        # claimed_auth_event_map should be given iff the event is an outlier
-        assert bool(claimed_auth_event_map) == event.internal_metadata.outlier
+        # This method should only be used for non-outliers
+        assert not event.internal_metadata.outlier
 
+        # first of all, check that the event itself is valid.
         room_version = await self._store.get_room_version_id(event.room_id)
         room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
 
-        if claimed_auth_event_map:
-            # if we have a copy of the auth events from the event, use that as the
-            # basis for auth.
-            auth_events = claimed_auth_event_map
-        else:
-            # otherwise, we calculate what the auth events *should* be, and use that
-            prev_state_ids = await context.get_prev_state_ids()
-            auth_events_ids = self._event_auth_handler.compute_auth_events(
-                event, prev_state_ids, for_verification=True
-            )
-            auth_events_x = await self._store.get_events(auth_events_ids)
-            auth_events = {(e.type, e.state_key): e for e in auth_events_x.values()}
+        try:
+            validate_event_for_room_version(room_version_obj, event)
+        except AuthError as e:
+            logger.warning("While validating received event %r: %s", event, e)
+            # TODO: use a different rejected reason here?
+            context.rejected = RejectedReason.AUTH_ERROR
+            return context
+
+        # calculate what the auth events *should* be, to use as a basis for auth.
+        prev_state_ids = await context.get_prev_state_ids()
+        auth_events_ids = self._event_auth_handler.compute_auth_events(
+            event, prev_state_ids, for_verification=True
+        )
+        auth_events_x = await self._store.get_events(auth_events_ids)
+        calculated_auth_event_map = {
+            (e.type, e.state_key): e for e in auth_events_x.values()
+        }
 
         try:
             (
                 context,
                 auth_events_for_auth,
             ) = await self._update_auth_events_and_context_for_auth(
-                origin, event, context, auth_events
+                origin,
+                event,
+                context,
+                calculated_auth_event_map=calculated_auth_event_map,
             )
         except Exception:
             # We don't really mind if the above fails, so lets not fail
@@ -1289,24 +1302,17 @@ async def _check_event_auth(
                 "Ignoring failure and continuing processing of event.",
                 event.event_id,
             )
-            auth_events_for_auth = auth_events
+            auth_events_for_auth = calculated_auth_event_map
 
         try:
-            event_auth.check(room_version_obj, event, auth_events=auth_events_for_auth)
+            check_auth_rules_for_event(room_version_obj, event, auth_events_for_auth)
         except AuthError as e:
             logger.warning("Failed auth resolution for %r because %s", event, e)
             context.rejected = RejectedReason.AUTH_ERROR
+            return context
 
-        if not context.rejected:
-            await self._check_for_soft_fail(event, state, backfilled, origin=origin)
-            await self._maybe_kick_guest_users(event)
-
-        # If we are going to send this event over federation we precaclculate
-        # the joined hosts.
-        if event.internal_metadata.get_send_on_behalf_of():
-            await self._event_creation_handler.cache_joined_hosts_for_event(
-                event, context
-            )
+        await self._check_for_soft_fail(event, state, backfilled, origin=origin)
+        await self._maybe_kick_guest_users(event)
 
         return context
 
@@ -1404,7 +1410,7 @@ async def _check_for_soft_fail(
         }
 
         try:
-            event_auth.check(room_version_obj, event, auth_events=current_auth_events)
+            check_auth_rules_for_event(room_version_obj, event, current_auth_events)
         except AuthError as e:
             logger.warning(
                 "Soft-failing %r (from %s) because %s",
@@ -1425,7 +1431,7 @@ async def _update_auth_events_and_context_for_auth(
         origin: str,
         event: EventBase,
         context: EventContext,
-        input_auth_events: StateMap[EventBase],
+        calculated_auth_event_map: StateMap[EventBase],
     ) -> Tuple[EventContext, StateMap[EventBase]]:
         """Helper for _check_event_auth. See there for docs.
 
@@ -1443,19 +1449,17 @@ async def _update_auth_events_and_context_for_auth(
             event:
             context:
 
-            input_auth_events:
-                Map from (event_type, state_key) to event
-
-                Normally, our calculated auth_events based on the state of the room
-                at the event's position in the DAG, though occasionally (eg if the
-                event is an outlier), may be the auth events claimed by the remote
-                server.
+            calculated_auth_event_map:
+                Our calculated auth_events based on the state of the room
+                at the event's position in the DAG.
 
         Returns:
             updated context, updated auth event map
         """
-        # take a copy of input_auth_events before we modify it.
-        auth_events: MutableStateMap[EventBase] = dict(input_auth_events)
+        assert not event.internal_metadata.outlier
+
+        # take a copy of calculated_auth_event_map before we modify it.
+        auth_events: MutableStateMap[EventBase] = dict(calculated_auth_event_map)
 
         event_auth_events = set(event.auth_event_ids())
 
@@ -1475,6 +1479,11 @@ async def _update_auth_events_and_context_for_auth(
             logger.debug("Events %s are in the store", have_events)
             missing_auth.difference_update(have_events)
 
+        # missing_auth is now the set of event_ids which:
+        #  a. are listed in event.auth_events, *and*
+        #  b. are *not* part of our calculated auth events based on room state, *and*
+        #  c. are *not* yet in our database.
+
         if missing_auth:
             # If we don't have all the auth events, we need to get them.
             logger.info("auth_events contains unknown events: %s", missing_auth)
@@ -1496,19 +1505,31 @@ async def _update_auth_events_and_context_for_auth(
                     }
                 )
 
-        if event.internal_metadata.is_outlier():
-            # XXX: given that, for an outlier, we'll be working with the
-            # event's *claimed* auth events rather than those we calculated:
-            # (a) is there any point in this test, since different_auth below will
-            # obviously be empty
-            # (b) alternatively, why don't we do it earlier?
-            logger.info("Skipping auth_event fetch for outlier")
-            return context, auth_events
+        # auth_events now contains
+        #   1. our *calculated* auth events based on the room state, plus:
+        #   2. any events which:
+        #       a. are listed in `event.auth_events`, *and*
+        #       b. are not part of our calculated auth events, *and*
+        #       c. were not in our database before the call to /event_auth
+        #       d. have since been added to our database (most likely by /event_auth).
 
         different_auth = event_auth_events.difference(
             e.event_id for e in auth_events.values()
         )
 
+        # different_auth is the set of events which *are* in `event.auth_events`, but
+        # which are *not* in `auth_events`. Comparing with (2.) above, this means
+        # exclusively the set of `event.auth_events` which we already had in our
+        # database before any call to /event_auth.
+        #
+        # I'm reasonably sure that the fact that events returned by /event_auth are
+        # blindly added to auth_events (and hence excluded from different_auth) is a bug
+        # - though it's a very long-standing one (see
+        # https://github.com/matrix-org/synapse/commit/78015948a7febb18e000651f72f8f58830a55b93#diff-0bc92da3d703202f5b9be2d3f845e375f5b1a6bc6ba61705a8af9be1121f5e42R786
+        # from Jan 2015 which seems to add it, though it actually just moves it from
+        # elsewhere (before that, it gets lost in a mess of huge "various bug fixes"
+        # PRs).
+
         if not different_auth:
             return context, auth_events
 
diff --git a/synapse/handlers/identity.py b/synapse/handlers/identity.py
index 78630aca4..3f33bc98a 100644
--- a/synapse/handlers/identity.py
+++ b/synapse/handlers/identity.py
@@ -41,28 +41,27 @@
     valid_id_server_location,
 )
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class IdentityHandler(BaseHandler):
+class IdentityHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.store = hs.get_datastore()
         # An HTTP client for contacting trusted URLs.
         self.http_client = SimpleHttpClient(hs)
         # An HTTP client for contacting identity servers specified by clients.
         self.blacklisting_http_client = SimpleHttpClient(
-            hs, ip_blacklist=hs.config.federation_ip_range_blacklist
+            hs, ip_blacklist=hs.config.server.federation_ip_range_blacklist
         )
         self.federation_http_client = hs.get_federation_http_client()
         self.hs = hs
 
-        self.rewrite_identity_server_urls = hs.config.registration.rewrite_identity_server_urls
+        self.rewrite_identity_server_urls = (
+            hs.config.registration.rewrite_identity_server_urls
+        )
         self._enable_lookup = hs.config.registration.enable_3pid_lookup
 
         self._web_client_location = hs.config.email.invite_client_location
@@ -344,8 +343,8 @@ async def try_unbind_threepid_with_id_server(
         # the server we connect to.
         id_server_url = self.rewrite_id_server_url(id_server, add_https=True)
 
-        if self.hs.config.bind_new_user_emails_to_sydent:
-            id_server_url = self.hs.config.bind_new_user_emails_to_sydent
+        if self.hs.config.registration.bind_new_user_emails_to_sydent:
+            id_server_url = self.hs.config.registration.bind_new_user_emails_to_sydent
 
         url = "%s/_matrix/identity/api/v1/3pid/unbind" % (id_server_url,)
 
@@ -630,9 +629,15 @@ async def validate_threepid_session(
 
         # Try to validate as email
         if self.hs.config.email.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
+            # Remote emails will only be used if a valid identity server is provided.
+            assert (
+                self.hs.config.registration.account_threepid_delegate_email is not None
+            )
+
             # Ask our delegated email identity server
             validation_session = await self.threepid_from_creds(
-                self.hs.config.account_threepid_delegate_email, threepid_creds
+                self.hs.config.registration.account_threepid_delegate_email,
+                threepid_creds,
             )
         elif self.hs.config.email.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
             # Get a validated session matching these details
@@ -644,10 +649,11 @@ async def validate_threepid_session(
             return validation_session
 
         # Try to validate as msisdn
-        if self.hs.config.account_threepid_delegate_msisdn:
+        if self.hs.config.registration.account_threepid_delegate_msisdn:
             # Ask our delegated msisdn identity server
             validation_session = await self.threepid_from_creds(
-                self.hs.config.account_threepid_delegate_msisdn, threepid_creds
+                self.hs.config.registration.account_threepid_delegate_msisdn,
+                threepid_creds,
             )
 
         return validation_session
diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index 9ad39a65d..d4e455615 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -31,8 +31,6 @@
 from synapse.util.caches.response_cache import ResponseCache
 from synapse.visibility import filter_events_for_client
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -40,9 +38,11 @@
 logger = logging.getLogger(__name__)
 
 
-class InitialSyncHandler(BaseHandler):
+class InitialSyncHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
+        self.state_handler = hs.get_state_handler()
         self.hs = hs
         self.state = hs.get_state_handler()
         self.clock = hs.get_clock()
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index fd861e94f..4de9f4b82 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -16,6 +16,7 @@
 # limitations under the License.
 import logging
 import random
+from http import HTTPStatus
 from typing import TYPE_CHECKING, Any, Dict, List, Mapping, Optional, Tuple
 
 from canonicaljson import encode_canonical_json
@@ -39,9 +40,11 @@
     NotFoundError,
     ShadowBanError,
     SynapseError,
+    UnsupportedRoomVersionError,
 )
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersions
 from synapse.api.urls import ConsentURIBuilder
+from synapse.event_auth import validate_event_for_room_version
 from synapse.events import EventBase
 from synapse.events.builder import EventBuilder
 from synapse.events.snapshot import EventContext
@@ -59,8 +62,6 @@
 from synapse.util.metrics import measure_func
 from synapse.visibility import filter_events_for_client
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.events.third_party_rules import ThirdPartyEventRules
     from synapse.server import HomeServer
@@ -79,7 +80,7 @@ def __init__(self, hs: "HomeServer"):
         self.storage = hs.get_storage()
         self.state_store = self.storage.state
         self._event_serializer = hs.get_event_client_serializer()
-        self._ephemeral_events_enabled = hs.config.enable_ephemeral_messages
+        self._ephemeral_events_enabled = hs.config.server.enable_ephemeral_messages
 
         # The scheduled call to self._expire_event. None if no call is currently
         # scheduled.
@@ -413,7 +414,9 @@ def __init__(self, hs: "HomeServer"):
         self.server_name = hs.hostname
         self.notifier = hs.get_notifier()
         self.config = hs.config
-        self.require_membership_for_aliases = hs.config.require_membership_for_aliases
+        self.require_membership_for_aliases = (
+            hs.config.server.require_membership_for_aliases
+        )
         self._events_shard_config = self.config.worker.events_shard_config
         self._instance_name = hs.get_instance_name()
 
@@ -423,13 +426,12 @@ def __init__(self, hs: "HomeServer"):
             Membership.JOIN,
             Membership.KNOCK,
         }
-        if self.hs.config.include_profile_data_on_invite:
+        if self.hs.config.server.include_profile_data_on_invite:
             self.membership_types_to_include_profile_data_in.add(Membership.INVITE)
 
         self.send_event = ReplicationSendEventRestServlet.make_client(hs)
 
-        # This is only used to get at ratelimit function
-        self.base_handler = BaseHandler(hs)
+        self.request_ratelimiter = hs.get_request_ratelimiter()
 
         # We arbitrarily limit concurrent event creation for a room to 5.
         # This is to stop us from diverging history *too* much.
@@ -459,11 +461,11 @@ def __init__(self, hs: "HomeServer"):
         #
         self._rooms_to_exclude_from_dummy_event_insertion: Dict[str, int] = {}
         # The number of forward extremeities before a dummy event is sent.
-        self._dummy_events_threshold = hs.config.dummy_events_threshold
+        self._dummy_events_threshold = hs.config.server.dummy_events_threshold
 
         if (
             self.config.worker.run_background_tasks
-            and self.config.cleanup_extremities_with_dummy_events
+            and self.config.server.cleanup_extremities_with_dummy_events
         ):
             self.clock.looping_call(
                 lambda: run_as_background_process(
@@ -475,7 +477,7 @@ def __init__(self, hs: "HomeServer"):
 
         self._message_handler = hs.get_message_handler()
 
-        self._ephemeral_events_enabled = hs.config.enable_ephemeral_messages
+        self._ephemeral_events_enabled = hs.config.server.enable_ephemeral_messages
 
         self._external_cache = hs.get_external_cache()
 
@@ -549,16 +551,22 @@ async def create_event(
         await self.auth.check_auth_blocking(requester=requester)
 
         if event_dict["type"] == EventTypes.Create and event_dict["state_key"] == "":
-            room_version = event_dict["content"]["room_version"]
+            room_version_id = event_dict["content"]["room_version"]
+            room_version_obj = KNOWN_ROOM_VERSIONS.get(room_version_id)
+            if not room_version_obj:
+                # this can happen if support is withdrawn for a room version
+                raise UnsupportedRoomVersionError(room_version_id)
         else:
             try:
-                room_version = await self.store.get_room_version_id(
+                room_version_obj = await self.store.get_room_version(
                     event_dict["room_id"]
                 )
             except NotFoundError:
                 raise AuthError(403, "Unknown room")
 
-        builder = self.event_builder_factory.new(room_version, event_dict)
+        builder = self.event_builder_factory.for_room_version(
+            room_version_obj, event_dict
+        )
 
         self.validator.validate_builder(builder)
 
@@ -1064,9 +1072,17 @@ async def handle_new_client_event(
             EventTypes.Create,
             "",
         ):
-            room_version = event.content.get("room_version", RoomVersions.V1.identifier)
+            room_version_id = event.content.get(
+                "room_version", RoomVersions.V1.identifier
+            )
+            room_version_obj = KNOWN_ROOM_VERSIONS.get(room_version_id)
+            if not room_version_obj:
+                raise UnsupportedRoomVersionError(
+                    "Attempt to create a room with unsupported room version %s"
+                    % (room_version_id,)
+                )
         else:
-            room_version = await self.store.get_room_version_id(event.room_id)
+            room_version_obj = await self.store.get_room_version(event.room_id)
 
         if event.internal_metadata.is_out_of_band_membership():
             # the only sort of out-of-band-membership events we expect to see here are
@@ -1075,8 +1091,9 @@ async def handle_new_client_event(
             assert event.content["membership"] == Membership.LEAVE
         else:
             try:
-                await self._event_auth_handler.check_from_context(
-                    room_version, event, context
+                validate_event_for_room_version(room_version_obj, event)
+                await self._event_auth_handler.check_auth_rules_from_context(
+                    room_version_obj, event, context
                 )
             except AuthError as err:
                 logger.warning("Denying new event %r because %s", event, err)
@@ -1302,7 +1319,7 @@ async def persist_and_notify_client_event(
                     original_event and event.sender != original_event.sender
                 )
 
-            await self.base_handler.ratelimit(
+            await self.request_ratelimiter.ratelimit(
                 requester, is_admin_redaction=is_admin_redaction
             )
 
@@ -1456,6 +1473,39 @@ async def persist_and_notify_client_event(
             if prev_state_ids:
                 raise AuthError(403, "Changing the room create event is forbidden")
 
+        if event.type == EventTypes.MSC2716_INSERTION:
+            room_version = await self.store.get_room_version_id(event.room_id)
+            room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
+
+            create_event = await self.store.get_create_event_for_room(event.room_id)
+            room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR)
+
+            # Only check an insertion event if the room version
+            # supports it or the event is from the room creator.
+            if room_version_obj.msc2716_historical or (
+                self.config.experimental.msc2716_enabled
+                and event.sender == room_creator
+            ):
+                next_batch_id = event.content.get(
+                    EventContentFields.MSC2716_NEXT_BATCH_ID
+                )
+                conflicting_insertion_event_id = (
+                    await self.store.get_insertion_event_by_batch_id(
+                        event.room_id, next_batch_id
+                    )
+                )
+                if conflicting_insertion_event_id is not None:
+                    # The current insertion event that we're processing is invalid
+                    # because an insertion event already exists in the room with the
+                    # same next_batch_id. We can't allow multiple because the batch
+                    # pointing will get weird, e.g. we can't determine which insertion
+                    # event the batch event is pointing to.
+                    raise SynapseError(
+                        HTTPStatus.BAD_REQUEST,
+                        "Another insertion event already exists with the same next_batch_id",
+                        errcode=Codes.INVALID_PARAM,
+                    )
+
         # Mark any `m.historical` messages as backfilled so they don't appear
         # in `/sync` and have the proper decrementing `stream_ordering` as we import
         backfilled = False
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 08b93b3ec..176e4dfdd 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -85,23 +85,29 @@ def __init__(self, hs: "HomeServer"):
         self._purges_by_id: Dict[str, PurgeStatus] = {}
         self._event_serializer = hs.get_event_client_serializer()
 
-        self._retention_default_max_lifetime = hs.config.retention_default_max_lifetime
+        self._retention_default_max_lifetime = (
+            hs.config.server.retention_default_max_lifetime
+        )
 
-        self._retention_allowed_lifetime_min = hs.config.retention_allowed_lifetime_min
-        self._retention_allowed_lifetime_max = hs.config.retention_allowed_lifetime_max
+        self._retention_allowed_lifetime_min = (
+            hs.config.server.retention_allowed_lifetime_min
+        )
+        self._retention_allowed_lifetime_max = (
+            hs.config.server.retention_allowed_lifetime_max
+        )
 
-        if hs.config.worker.run_background_tasks and hs.config.retention_enabled:
+        if hs.config.worker.run_background_tasks and hs.config.server.retention_enabled:
             # Run the purge jobs described in the configuration file.
-            for job in hs.config.retention_purge_jobs:
+            for job in hs.config.server.retention_purge_jobs:
                 logger.info("Setting up purge job with config: %s", job)
 
                 self.clock.looping_call(
                     run_as_background_process,
-                    job["interval"],
+                    job.interval,
                     "purge_history_for_rooms_in_range",
                     self.purge_history_for_rooms_in_range,
-                    job["shortest_max_lifetime"],
-                    job["longest_max_lifetime"],
+                    job.shortest_max_lifetime,
+                    job.longest_max_lifetime,
                 )
 
     async def purge_history_for_rooms_in_range(
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index 8c44ca5f2..86639b0ce 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -19,6 +19,7 @@
 from signedjson.sign import sign_json
 
 from twisted.internet import reactor
+from twisted.internet.defer import Deferred
 
 from synapse.api.errors import (
     AuthError,
@@ -41,8 +42,6 @@
     get_domain_from_id,
 )
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -52,7 +51,7 @@
 MAX_AVATAR_URL_LEN = 1000
 
 
-class ProfileHandler(BaseHandler):
+class ProfileHandler:
     """Handles fetching and updating user profile information.
 
     ProfileHandler can be instantiated directly on workers and will
@@ -65,7 +64,9 @@ class ProfileHandler(BaseHandler):
     PROFILE_REPLICATE_INTERVAL = 2 * 60 * 1000
 
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self.hs = hs
 
         self.federation = hs.get_federation_client()
         hs.get_federation_registry().register_query_handler(
@@ -73,19 +74,22 @@ def __init__(self, hs: "HomeServer"):
         )
 
         self.user_directory_handler = hs.get_user_directory_handler()
+        self.request_ratelimiter = hs.get_request_ratelimiter()
 
         self.http_client = hs.get_simple_http_client()
 
-        self.max_avatar_size = hs.config.max_avatar_size
-        self.allowed_avatar_mimetypes = hs.config.allowed_avatar_mimetypes
-        self.replicate_user_profiles_to = hs.config.replicate_user_profiles_to
+        self.max_avatar_size = hs.config.media.max_avatar_size
+        self.allowed_avatar_mimetypes = hs.config.media.allowed_avatar_mimetypes
+        self.replicate_user_profiles_to = (
+            hs.config.registration.replicate_user_profiles_to
+        )
 
         if hs.config.worker.run_background_tasks:
             self.clock.looping_call(
                 self._update_remote_profile_cache, self.PROFILE_UPDATE_MS
             )
 
-            if len(self.hs.config.replicate_user_profiles_to) > 0:
+            if len(self.replicate_user_profiles_to) > 0:
                 reactor.callWhenRunning(self._do_assign_profile_replication_batches)  # type: ignore
                 reactor.callWhenRunning(self._start_replicate_profiles)  # type: ignore
                 # Add a looping call to replicate_profiles: this handles retries
@@ -95,18 +99,18 @@ def __init__(self, hs: "HomeServer"):
                     self._start_replicate_profiles, self.PROFILE_REPLICATE_INTERVAL
                 )
 
-    def _do_assign_profile_replication_batches(self):
+    def _do_assign_profile_replication_batches(self) -> Deferred:
         return run_as_background_process(
             "_assign_profile_replication_batches",
             self._assign_profile_replication_batches,
         )
 
-    def _start_replicate_profiles(self):
+    def _start_replicate_profiles(self) -> Deferred:
         return run_as_background_process(
             "_replicate_profiles", self._replicate_profiles
         )
 
-    async def _assign_profile_replication_batches(self):
+    async def _assign_profile_replication_batches(self) -> None:
         """If no profile replication has been done yet, allocate replication batch
         numbers to each profile to start the replication process.
         """
@@ -119,7 +123,7 @@ async def _assign_profile_replication_batches(self):
                 break
         logger.info("Assigned %d profile batch numbers", total)
 
-    async def _replicate_profiles(self):
+    async def _replicate_profiles(self) -> None:
         """If any profile data has been updated and not pushed to the replication targets,
         replicate it.
         """
@@ -127,7 +131,7 @@ async def _replicate_profiles(self):
         latest_batch = await self.store.get_latest_profile_replication_batch_number()
         if latest_batch is None:
             latest_batch = -1
-        for repl_host in self.hs.config.replicate_user_profiles_to:
+        for repl_host in self.replicate_user_profiles_to:
             if repl_host not in host_batches:
                 host_batches[repl_host] = -1
             try:
@@ -138,7 +142,7 @@ async def _replicate_profiles(self):
                     "Exception while replicating to %s: aborting for now", repl_host
                 )
 
-    async def _replicate_host_profile_batch(self, host, batchnum):
+    async def _replicate_host_profile_batch(self, host: str, batchnum: int) -> None:
         logger.info("Replicating profile batch %d to %s", batchnum, host)
         batch_rows = await self.store.get_profile_batch(batchnum)
         batch = {
@@ -152,7 +156,9 @@ async def _replicate_host_profile_batch(self, host, batchnum):
 
         url = "https://%s/_matrix/identity/api/v1/replicate_profiles" % (host,)
         body = {"batchnum": batchnum, "batch": batch, "origin_server": self.hs.hostname}
-        signed_body = sign_json(body, self.hs.hostname, self.hs.config.signing_key[0])
+        signed_body = sign_json(
+            body, self.hs.hostname, self.hs.config.key.signing_key[0]
+        )
         try:
             await self.http_client.post_json_get_json(url, signed_body)
             await self.store.update_replication_batch_for_host(host, batchnum)
@@ -276,7 +282,7 @@ async def set_displayname(
         if not by_admin and target_user != requester.user:
             raise AuthError(400, "Cannot set another user's displayname")
 
-        if not by_admin and not self.hs.config.enable_set_displayname:
+        if not by_admin and not self.hs.config.registration.enable_set_displayname:
             profile = await self.store.get_profileinfo(target_user.localpart)
             if profile.display_name:
                 raise SynapseError(
@@ -308,7 +314,7 @@ async def set_displayname(
                 authenticated_entity=requester.authenticated_entity,
             )
 
-        if len(self.hs.config.replicate_user_profiles_to) > 0:
+        if len(self.replicate_user_profiles_to) > 0:
             cur_batchnum = (
                 await self.store.get_latest_profile_replication_batch_number()
             )
@@ -338,7 +344,7 @@ async def set_active(
         users: List[UserID],
         active: bool,
         hide: bool,
-    ):
+    ) -> None:
         """
         Sets the 'active' flag on a set of user profiles. If set to false, the
         accounts are considered deactivated or hidden.
@@ -420,7 +426,7 @@ async def set_avatar_url(
         if not by_admin and target_user != requester.user:
             raise AuthError(400, "Cannot set another user's avatar_url")
 
-        if not by_admin and not self.hs.config.enable_set_avatar_url:
+        if not by_admin and not self.hs.config.registration.enable_set_avatar_url:
             profile = await self.store.get_profileinfo(target_user.localpart)
             if profile.avatar_url:
                 raise SynapseError(
@@ -481,7 +487,7 @@ async def set_avatar_url(
                 target_user, authenticated_entity=requester.authenticated_entity
             )
 
-        if len(self.hs.config.replicate_user_profiles_to) > 0:
+        if len(self.replicate_user_profiles_to) > 0:
             cur_batchnum = (
                 await self.store.get_latest_profile_replication_batch_number()
             )
@@ -503,14 +509,14 @@ async def set_avatar_url(
         # start a profile replication push
         run_in_background(self._replicate_profiles)
 
-    def _validate_and_parse_media_id_from_avatar_url(self, mxc):
+    def _validate_and_parse_media_id_from_avatar_url(self, mxc: str) -> str:
         """Validate and parse a provided avatar url and return the local media id
 
         Args:
-            mxc (str): A mxc URL
+            mxc: A mxc URL
 
         Returns:
-            str: The ID of the media
+            The ID of the media
         """
         avatar_pieces = mxc.split("/")
         if len(avatar_pieces) != 4 or avatar_pieces[0] != "mxc:":
@@ -561,7 +567,7 @@ async def _update_join_states(
             return
 
         if ratelimit:
-            await self.ratelimit(requester)
+            await self.request_ratelimiter.ratelimit(requester)
 
         # Do not actually update the room state for shadow-banned users.
         if requester.shadow_banned:
@@ -612,7 +618,7 @@ async def check_profile_query_allowed(
         # when building a membership event. In this case, we must allow the
         # lookup.
         if (
-            not self.hs.config.limit_profile_requests_to_users_who_share_rooms
+            not self.hs.config.server.limit_profile_requests_to_users_who_share_rooms
             or not requester
         ):
             return
diff --git a/synapse/handlers/read_marker.py b/synapse/handlers/read_marker.py
index bd8160e7e..58593e570 100644
--- a/synapse/handlers/read_marker.py
+++ b/synapse/handlers/read_marker.py
@@ -17,17 +17,14 @@
 
 from synapse.util.async_helpers import Linearizer
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class ReadMarkerHandler(BaseHandler):
+class ReadMarkerHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
         self.server_name = hs.config.server.server_name
         self.store = hs.get_datastore()
         self.account_data_handler = hs.get_account_data_handler()
diff --git a/synapse/handlers/receipts.py b/synapse/handlers/receipts.py
index f21f33ada..374e961e3 100644
--- a/synapse/handlers/receipts.py
+++ b/synapse/handlers/receipts.py
@@ -16,7 +16,6 @@
 
 from synapse.api.constants import ReadReceiptEventFields
 from synapse.appservice import ApplicationService
-from synapse.handlers._base import BaseHandler
 from synapse.streams import EventSource
 from synapse.types import JsonDict, ReadReceipt, UserID, get_domain_from_id
 
@@ -26,10 +25,9 @@
 logger = logging.getLogger(__name__)
 
 
-class ReceiptsHandler(BaseHandler):
+class ReceiptsHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.notifier = hs.get_notifier()
         self.server_name = hs.config.server.server_name
         self.store = hs.get_datastore()
         self.event_auth_handler = hs.get_event_auth_handler()
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 9a0eefec5..5d03dc281 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -41,8 +41,6 @@
 from synapse.storage.state import StateFilter
 from synapse.types import RoomAlias, UserID, create_requester
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -85,9 +83,10 @@ class LoginDict(TypedDict):
     refresh_token: Optional[str]
 
 
-class RegistrationHandler(BaseHandler):
+class RegistrationHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
         self.hs = hs
         self.auth = hs.get_auth()
         self._auth_handler = hs.get_auth_handler()
@@ -104,7 +103,9 @@ def __init__(self, hs: "HomeServer"):
 
         self.spam_checker = hs.get_spam_checker()
 
-        self._show_in_user_directory = self.hs.config.show_users_in_user_directory
+        self._show_in_user_directory = (
+            self.hs.config.server.show_users_in_user_directory
+        )
 
         if hs.config.worker.worker_app:
             self._register_client = ReplicationRegisterServlet.make_client(hs)
@@ -119,8 +120,8 @@ def __init__(self, hs: "HomeServer"):
             self._register_device_client = self.register_device_inner
             self.pusher_pool = hs.get_pusherpool()
 
-        self.session_lifetime = hs.config.session_lifetime
-        self.access_token_lifetime = hs.config.access_token_lifetime
+        self.session_lifetime = hs.config.registration.session_lifetime
+        self.access_token_lifetime = hs.config.registration.access_token_lifetime
 
         init_counters_for_auth_provider("")
 
@@ -358,8 +359,13 @@ async def register_user(
             auth_provider=(auth_provider_id or ""),
         ).inc()
 
+        # If the user does not need to consent at registration, auto-join any
+        # configured rooms.
         if not self.hs.config.consent.user_consent_at_registration:
-            if not self.hs.config.auto_join_rooms_for_guests and make_guest:
+            if (
+                not self.hs.config.registration.auto_join_rooms_for_guests
+                and make_guest
+            ):
                 logger.info(
                     "Skipping auto-join for %s because auto-join for guests is disabled",
                     user_id,
@@ -413,7 +419,7 @@ async def _create_and_join_rooms(self, user_id: str) -> None:
             "preset": self.hs.config.registration.autocreate_auto_join_room_preset,
         }
 
-        # If the configuration providers a user ID to create rooms with, use
+        # If the configuration provides a user ID to create rooms with, use
         # that instead of the first user registered.
         requires_join = False
         if self.hs.config.registration.auto_join_user_id:
@@ -536,7 +542,7 @@ async def _join_rooms(self, user_id: str) -> None:
                 # we don't have a local user in the room to craft up an invite with.
                 requires_invite = await self.store.is_host_joined(
                     room_id,
-                    self.server_name,
+                    self._server_name,
                 )
 
                 if requires_invite:
@@ -882,22 +888,24 @@ async def post_registration_actions(
             # Necessary due to auth checks prior to the threepid being
             # written to the db
             if is_threepid_reserved(
-                self.hs.config.mau_limits_reserved_threepids, threepid
+                self.hs.config.server.mau_limits_reserved_threepids, threepid
             ):
                 await self.store.upsert_monthly_active_user(user_id)
 
             await self.register_email_threepid(user_id, threepid, access_token)
 
-            if self.hs.config.bind_new_user_emails_to_sydent:
+            if self.hs.config.registration.bind_new_user_emails_to_sydent:
                 # Attempt to call Sydent's internal bind API on the given identity server
                 # to bind this threepid
-                id_server_url = self.hs.config.bind_new_user_emails_to_sydent
+                id_server_url = (
+                    self.hs.config.registration.bind_new_user_emails_to_sydent
+                )
 
                 logger.debug(
                     "Attempting the bind email of %s to identity server: %s using "
                     "internal Sydent bind API.",
                     user_id,
-                    self.hs.config.bind_new_user_emails_to_sydent,
+                    self.hs.config.registration.bind_new_user_emails_to_sydent,
                 )
 
                 try:
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 37d03b796..7072bca1f 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -52,6 +52,7 @@
 )
 from synapse.api.filtering import Filter
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
+from synapse.event_auth import validate_event_for_room_version
 from synapse.events import EventBase
 from synapse.events.utils import copy_power_levels_contents
 from synapse.rest.admin._base import assert_user_is_admin
@@ -75,8 +76,6 @@
 from synapse.util.stringutils import parse_and_validate_server_name
 from synapse.visibility import filter_events_for_client
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -87,15 +86,18 @@
 FIVE_MINUTES_IN_MS = 5 * 60 * 1000
 
 
-class RoomCreationHandler(BaseHandler):
+class RoomCreationHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
-
+        self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.hs = hs
         self.spam_checker = hs.get_spam_checker()
         self.event_creation_handler = hs.get_event_creation_handler()
         self.room_member_handler = hs.get_room_member_handler()
         self._event_auth_handler = hs.get_event_auth_handler()
         self.config = hs.config
+        self.request_ratelimiter = hs.get_request_ratelimiter()
 
         # Room state based off defined presets
         self._presets_dict: Dict[str, Dict[str, Any]] = {
@@ -161,7 +163,7 @@ async def upgrade_room(
         Raises:
             ShadowBanError if the requester is shadow-banned.
         """
-        await self.ratelimit(requester)
+        await self.request_ratelimiter.ratelimit(requester)
 
         user_id = requester.user.to_string()
 
@@ -237,8 +239,9 @@ async def _upgrade_room(
                 },
             },
         )
-        old_room_version = await self.store.get_room_version_id(old_room_id)
-        await self._event_auth_handler.check_from_context(
+        old_room_version = await self.store.get_room_version(old_room_id)
+        validate_event_for_room_version(old_room_version, tombstone_event)
+        await self._event_auth_handler.check_auth_rules_from_context(
             old_room_version, tombstone_event, tombstone_context
         )
 
@@ -663,10 +666,10 @@ async def create_room(
             raise SynapseError(403, "You are not permitted to create rooms")
 
         if ratelimit:
-            await self.ratelimit(requester)
+            await self.request_ratelimiter.ratelimit(requester)
 
         room_version_id = config.get(
-            "room_version", self.config.default_room_version.identifier
+            "room_version", self.config.server.default_room_version.identifier
         )
 
         if not isinstance(room_version_id, str):
diff --git a/synapse/handlers/room_batch.py b/synapse/handlers/room_batch.py
new file mode 100644
index 000000000..51dd4e755
--- /dev/null
+++ b/synapse/handlers/room_batch.py
@@ -0,0 +1,423 @@
+import logging
+from typing import TYPE_CHECKING, List, Tuple
+
+from synapse.api.constants import EventContentFields, EventTypes
+from synapse.appservice import ApplicationService
+from synapse.http.servlet import assert_params_in_dict
+from synapse.types import JsonDict, Requester, UserID, create_requester
+from synapse.util.stringutils import random_string
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class RoomBatchHandler:
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+        self.store = hs.get_datastore()
+        self.state_store = hs.get_storage().state
+        self.event_creation_handler = hs.get_event_creation_handler()
+        self.room_member_handler = hs.get_room_member_handler()
+        self.auth = hs.get_auth()
+
+    async def inherit_depth_from_prev_ids(self, prev_event_ids: List[str]) -> int:
+        """Finds the depth which would sort it after the most-recent
+        prev_event_id but before the successors of those events. If no
+        successors are found, we assume it's an historical extremity part of the
+        current batch and use the same depth of the prev_event_ids.
+
+        Args:
+            prev_event_ids: List of prev event IDs
+
+        Returns:
+            Inherited depth
+        """
+        (
+            most_recent_prev_event_id,
+            most_recent_prev_event_depth,
+        ) = await self.store.get_max_depth_of(prev_event_ids)
+
+        # We want to insert the historical event after the `prev_event` but before the successor event
+        #
+        # We inherit depth from the successor event instead of the `prev_event`
+        # because events returned from `/messages` are first sorted by `topological_ordering`
+        # which is just the `depth` and then tie-break with `stream_ordering`.
+        #
+        # We mark these inserted historical events as "backfilled" which gives them a
+        # negative `stream_ordering`. If we use the same depth as the `prev_event`,
+        # then our historical event will tie-break and be sorted before the `prev_event`
+        # when it should come after.
+        #
+        # We want to use the successor event depth so they appear after `prev_event` because
+        # it has a larger `depth` but before the successor event because the `stream_ordering`
+        # is negative before the successor event.
+        successor_event_ids = await self.store.get_successor_events(
+            [most_recent_prev_event_id]
+        )
+
+        # If we can't find any successor events, then it's a forward extremity of
+        # historical messages and we can just inherit from the previous historical
+        # event which we can already assume has the correct depth where we want
+        # to insert into.
+        if not successor_event_ids:
+            depth = most_recent_prev_event_depth
+        else:
+            (
+                _,
+                oldest_successor_depth,
+            ) = await self.store.get_min_depth_of(successor_event_ids)
+
+            depth = oldest_successor_depth
+
+        return depth
+
+    def create_insertion_event_dict(
+        self, sender: str, room_id: str, origin_server_ts: int
+    ) -> JsonDict:
+        """Creates an event dict for an "insertion" event with the proper fields
+        and a random batch ID.
+
+        Args:
+            sender: The event author MXID
+            room_id: The room ID that the event belongs to
+            origin_server_ts: Timestamp when the event was sent
+
+        Returns:
+            The new event dictionary to insert.
+        """
+
+        next_batch_id = random_string(8)
+        insertion_event = {
+            "type": EventTypes.MSC2716_INSERTION,
+            "sender": sender,
+            "room_id": room_id,
+            "content": {
+                EventContentFields.MSC2716_NEXT_BATCH_ID: next_batch_id,
+                EventContentFields.MSC2716_HISTORICAL: True,
+            },
+            "origin_server_ts": origin_server_ts,
+        }
+
+        return insertion_event
+
+    async def create_requester_for_user_id_from_app_service(
+        self, user_id: str, app_service: ApplicationService
+    ) -> Requester:
+        """Creates a new requester for the given user_id
+        and validates that the app service is allowed to control
+        the given user.
+
+        Args:
+            user_id: The author MXID that the app service is controlling
+            app_service: The app service that controls the user
+
+        Returns:
+            Requester object
+        """
+
+        await self.auth.validate_appservice_can_control_user_id(app_service, user_id)
+
+        return create_requester(user_id, app_service=app_service)
+
+    async def get_most_recent_auth_event_ids_from_event_id_list(
+        self, event_ids: List[str]
+    ) -> List[str]:
+        """Find the most recent auth event ids (derived from state events) that
+        allowed that message to be sent. We will use this as a base
+        to auth our historical messages against.
+
+        Args:
+            event_ids: List of event ID's to look at
+
+        Returns:
+            List of event ID's
+        """
+
+        (
+            most_recent_prev_event_id,
+            _,
+        ) = await self.store.get_max_depth_of(event_ids)
+        # mapping from (type, state_key) -> state_event_id
+        prev_state_map = await self.state_store.get_state_ids_for_event(
+            most_recent_prev_event_id
+        )
+        # List of state event ID's
+        prev_state_ids = list(prev_state_map.values())
+        auth_event_ids = prev_state_ids
+
+        return auth_event_ids
+
+    async def persist_state_events_at_start(
+        self,
+        state_events_at_start: List[JsonDict],
+        room_id: str,
+        initial_auth_event_ids: List[str],
+        app_service_requester: Requester,
+    ) -> List[str]:
+        """Takes all `state_events_at_start` event dictionaries and creates/persists
+        them as floating state events which don't resolve into the current room state.
+        They are floating because they reference a fake prev_event which doesn't connect
+        to the normal DAG at all.
+
+        Args:
+            state_events_at_start:
+            room_id: Room where you want the events persisted in.
+            initial_auth_event_ids: These will be the auth_events for the first
+                state event created. Each event created afterwards will be
+                added to the list of auth events for the next state event
+                created.
+            app_service_requester: The requester of an application service.
+
+        Returns:
+            List of state event ID's we just persisted
+        """
+        assert app_service_requester.app_service
+
+        state_event_ids_at_start = []
+        auth_event_ids = initial_auth_event_ids.copy()
+        for state_event in state_events_at_start:
+            assert_params_in_dict(
+                state_event, ["type", "origin_server_ts", "content", "sender"]
+            )
+
+            logger.debug(
+                "RoomBatchSendEventRestServlet inserting state_event=%s, auth_event_ids=%s",
+                state_event,
+                auth_event_ids,
+            )
+
+            event_dict = {
+                "type": state_event["type"],
+                "origin_server_ts": state_event["origin_server_ts"],
+                "content": state_event["content"],
+                "room_id": room_id,
+                "sender": state_event["sender"],
+                "state_key": state_event["state_key"],
+            }
+
+            # Mark all events as historical
+            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
+
+            # Make the state events float off on their own so we don't have a
+            # bunch of `@mxid joined the room` noise between each batch
+            fake_prev_event_id = "$" + random_string(43)
+
+            # TODO: This is pretty much the same as some other code to handle inserting state in this file
+            if event_dict["type"] == EventTypes.Member:
+                membership = event_dict["content"].get("membership", None)
+                event_id, _ = await self.room_member_handler.update_membership(
+                    await self.create_requester_for_user_id_from_app_service(
+                        state_event["sender"], app_service_requester.app_service
+                    ),
+                    target=UserID.from_string(event_dict["state_key"]),
+                    room_id=room_id,
+                    action=membership,
+                    content=event_dict["content"],
+                    outlier=True,
+                    prev_event_ids=[fake_prev_event_id],
+                    # Make sure to use a copy of this list because we modify it
+                    # later in the loop here. Otherwise it will be the same
+                    # reference and also update in the event when we append later.
+                    auth_event_ids=auth_event_ids.copy(),
+                )
+            else:
+                # TODO: Add some complement tests that adds state that is not member joins
+                # and will use this code path. Maybe we only want to support join state events
+                # and can get rid of this `else`?
+                (
+                    event,
+                    _,
+                ) = await self.event_creation_handler.create_and_send_nonmember_event(
+                    await self.create_requester_for_user_id_from_app_service(
+                        state_event["sender"], app_service_requester.app_service
+                    ),
+                    event_dict,
+                    outlier=True,
+                    prev_event_ids=[fake_prev_event_id],
+                    # Make sure to use a copy of this list because we modify it
+                    # later in the loop here. Otherwise it will be the same
+                    # reference and also update in the event when we append later.
+                    auth_event_ids=auth_event_ids.copy(),
+                )
+                event_id = event.event_id
+
+            state_event_ids_at_start.append(event_id)
+            auth_event_ids.append(event_id)
+
+        return state_event_ids_at_start
+
+    async def persist_historical_events(
+        self,
+        events_to_create: List[JsonDict],
+        room_id: str,
+        initial_prev_event_ids: List[str],
+        inherited_depth: int,
+        auth_event_ids: List[str],
+        app_service_requester: Requester,
+    ) -> List[str]:
+        """Create and persists all events provided sequentially. Handles the
+        complexity of creating events in chronological order so they can
+        reference each other by prev_event but still persists in
+        reverse-chronoloical order so they have the correct
+        (topological_ordering, stream_ordering) and sort correctly from
+        /messages.
+
+        Args:
+            events_to_create: List of historical events to create in JSON
+                dictionary format.
+            room_id: Room where you want the events persisted in.
+            initial_prev_event_ids: These will be the prev_events for the first
+                event created. Each event created afterwards will point to the
+                previous event created.
+            inherited_depth: The depth to create the events at (you will
+                probably by calling inherit_depth_from_prev_ids(...)).
+            auth_event_ids: Define which events allow you to create the given
+                event in the room.
+            app_service_requester: The requester of an application service.
+
+        Returns:
+            List of persisted event IDs
+        """
+        assert app_service_requester.app_service
+
+        prev_event_ids = initial_prev_event_ids.copy()
+
+        event_ids = []
+        events_to_persist = []
+        for ev in events_to_create:
+            assert_params_in_dict(ev, ["type", "origin_server_ts", "content", "sender"])
+
+            event_dict = {
+                "type": ev["type"],
+                "origin_server_ts": ev["origin_server_ts"],
+                "content": ev["content"],
+                "room_id": room_id,
+                "sender": ev["sender"],  # requester.user.to_string(),
+                "prev_events": prev_event_ids.copy(),
+            }
+
+            # Mark all events as historical
+            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
+
+            event, context = await self.event_creation_handler.create_event(
+                await self.create_requester_for_user_id_from_app_service(
+                    ev["sender"], app_service_requester.app_service
+                ),
+                event_dict,
+                prev_event_ids=event_dict.get("prev_events"),
+                auth_event_ids=auth_event_ids,
+                historical=True,
+                depth=inherited_depth,
+            )
+            logger.debug(
+                "RoomBatchSendEventRestServlet inserting event=%s, prev_event_ids=%s, auth_event_ids=%s",
+                event,
+                prev_event_ids,
+                auth_event_ids,
+            )
+
+            assert self.hs.is_mine_id(event.sender), "User must be our own: %s" % (
+                event.sender,
+            )
+
+            events_to_persist.append((event, context))
+            event_id = event.event_id
+
+            event_ids.append(event_id)
+            prev_event_ids = [event_id]
+
+        # Persist events in reverse-chronological order so they have the
+        # correct stream_ordering as they are backfilled (which decrements).
+        # Events are sorted by (topological_ordering, stream_ordering)
+        # where topological_ordering is just depth.
+        for (event, context) in reversed(events_to_persist):
+            await self.event_creation_handler.handle_new_client_event(
+                await self.create_requester_for_user_id_from_app_service(
+                    event["sender"], app_service_requester.app_service
+                ),
+                event=event,
+                context=context,
+            )
+
+        return event_ids
+
+    async def handle_batch_of_events(
+        self,
+        events_to_create: List[JsonDict],
+        room_id: str,
+        batch_id_to_connect_to: str,
+        initial_prev_event_ids: List[str],
+        inherited_depth: int,
+        auth_event_ids: List[str],
+        app_service_requester: Requester,
+    ) -> Tuple[List[str], str]:
+        """
+        Handles creating and persisting all of the historical events as well
+        as insertion and batch meta events to make the batch navigable in the DAG.
+
+        Args:
+            events_to_create: List of historical events to create in JSON
+                dictionary format.
+            room_id: Room where you want the events created in.
+            batch_id_to_connect_to: The batch_id from the insertion event you
+                want this batch to connect to.
+            initial_prev_event_ids: These will be the prev_events for the first
+                event created. Each event created afterwards will point to the
+                previous event created.
+            inherited_depth: The depth to create the events at (you will
+                probably by calling inherit_depth_from_prev_ids(...)).
+            auth_event_ids: Define which events allow you to create the given
+                event in the room.
+            app_service_requester: The requester of an application service.
+
+        Returns:
+            Tuple containing a list of created events and the next_batch_id
+        """
+
+        # Connect this current batch to the insertion event from the previous batch
+        last_event_in_batch = events_to_create[-1]
+        batch_event = {
+            "type": EventTypes.MSC2716_BATCH,
+            "sender": app_service_requester.user.to_string(),
+            "room_id": room_id,
+            "content": {
+                EventContentFields.MSC2716_BATCH_ID: batch_id_to_connect_to,
+                EventContentFields.MSC2716_HISTORICAL: True,
+            },
+            # Since the batch event is put at the end of the batch,
+            # where the newest-in-time event is, copy the origin_server_ts from
+            # the last event we're inserting
+            "origin_server_ts": last_event_in_batch["origin_server_ts"],
+        }
+        # Add the batch event to the end of the batch (newest-in-time)
+        events_to_create.append(batch_event)
+
+        # Add an "insertion" event to the start of each batch (next to the oldest-in-time
+        # event in the batch) so the next batch can be connected to this one.
+        insertion_event = self.create_insertion_event_dict(
+            sender=app_service_requester.user.to_string(),
+            room_id=room_id,
+            # Since the insertion event is put at the start of the batch,
+            # where the oldest-in-time event is, copy the origin_server_ts from
+            # the first event we're inserting
+            origin_server_ts=events_to_create[0]["origin_server_ts"],
+        )
+        next_batch_id = insertion_event["content"][
+            EventContentFields.MSC2716_NEXT_BATCH_ID
+        ]
+        # Prepend the insertion event to the start of the batch (oldest-in-time)
+        events_to_create = [insertion_event] + events_to_create
+
+        # Create and persist all of the historical events
+        event_ids = await self.persist_historical_events(
+            events_to_create=events_to_create,
+            room_id=room_id,
+            initial_prev_event_ids=initial_prev_event_ids,
+            inherited_depth=inherited_depth,
+            auth_event_ids=auth_event_ids,
+            app_service_requester=app_service_requester,
+        )
+
+        return event_ids, next_batch_id
diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index c3d4199ed..ba7a14d65 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -36,8 +36,6 @@
 from synapse.util.caches.descriptors import _CacheContext, cached
 from synapse.util.caches.response_cache import ResponseCache
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -49,9 +47,10 @@
 EMPTY_THIRD_PARTY_ID = ThirdPartyInstanceID(None, None)
 
 
-class RoomListHandler(BaseHandler):
+class RoomListHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
+        self.hs = hs
         self.enable_room_list_search = hs.config.roomdirectory.enable_room_list_search
         self.response_cache: ResponseCache[
             Tuple[Optional[int], Optional[str], Optional[ThirdPartyInstanceID]]
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index b50b88140..8fcab486d 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -51,8 +51,6 @@
 from synapse.util.async_helpers import Linearizer
 from synapse.util.distributor import user_left_room
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -89,8 +87,8 @@ def __init__(self, hs: "HomeServer"):
         self.spam_checker = hs.get_spam_checker()
         self.third_party_event_rules = hs.get_third_party_event_rules()
         self._server_notices_mxid = self.config.servernotices.server_notices_mxid
-        self._enable_lookup = hs.config.enable_3pid_lookup
-        self.allow_per_room_profiles = self.config.allow_per_room_profiles
+        self._enable_lookup = hs.config.registration.enable_3pid_lookup
+        self.allow_per_room_profiles = self.config.server.allow_per_room_profiles
 
         self._join_rate_limiter_local = Ratelimiter(
             store=self.store,
@@ -118,9 +116,7 @@ def __init__(self, hs: "HomeServer"):
             burst_count=hs.config.ratelimiting.rc_invites_per_user.burst_count,
         )
 
-        # This is only used to get at the ratelimit function. It's fine there are
-        # multiple of these as it doesn't store state.
-        self.base_handler = BaseHandler(hs)
+        self.request_ratelimiter = hs.get_request_ratelimiter()
 
     @abc.abstractmethod
     async def _remote_join(
@@ -632,7 +628,7 @@ async def update_membership_locked(
                 is_requester_admin = await self.auth.is_server_admin(requester.user)
 
             if not is_requester_admin:
-                if self.config.block_non_admin_invites:
+                if self.config.server.block_non_admin_invites:
                     logger.info(
                         "Blocking invite: user is not admin and non-admin "
                         "invites disabled"
@@ -1261,7 +1257,7 @@ async def do_3pid_invite(
         Raises:
             ShadowBanError if the requester has been shadow-banned.
         """
-        if self.config.block_non_admin_invites:
+        if self.config.server.block_non_admin_invites:
             is_requester_admin = await self.auth.is_server_admin(requester.user)
             if not is_requester_admin:
                 raise SynapseError(
@@ -1275,7 +1271,7 @@ async def do_3pid_invite(
 
         # We need to rate limit *before* we send out any 3PID invites, so we
         # can't just rely on the standard ratelimiting of events.
-        await self.base_handler.ratelimit(requester)
+        await self.request_ratelimiter.ratelimit(requester)
 
         can_invite = await self.third_party_event_rules.check_threepid_can_be_invited(
             medium, address, room_id
@@ -1481,7 +1477,7 @@ async def _is_remote_room_too_complex(
         Returns: bool of whether the complexity is too great, or None
             if unable to be fetched
         """
-        max_complexity = self.hs.config.limit_remote_rooms.complexity
+        max_complexity = self.hs.config.server.limit_remote_rooms.complexity
         complexity = await self.federation_handler.get_room_complexity(
             remote_room_hosts, room_id
         )
@@ -1497,7 +1493,7 @@ async def _is_local_room_too_complex(self, room_id: str) -> bool:
         Args:
             room_id: The room ID to check for complexity.
         """
-        max_complexity = self.hs.config.limit_remote_rooms.complexity
+        max_complexity = self.hs.config.server.limit_remote_rooms.complexity
         complexity = await self.store.get_room_complexity(room_id)
 
         return complexity["v1"] > max_complexity
@@ -1521,8 +1517,11 @@ async def _remote_join(
         if len(remote_room_hosts) == 0:
             raise SynapseError(404, "No known servers")
 
-        check_complexity = self.hs.config.limit_remote_rooms.enabled
-        if check_complexity and self.hs.config.limit_remote_rooms.admins_can_join:
+        check_complexity = self.hs.config.server.limit_remote_rooms.enabled
+        if (
+            check_complexity
+            and self.hs.config.server.limit_remote_rooms.admins_can_join
+        ):
             check_complexity = not await self.auth.is_server_admin(user)
 
         if check_complexity:
@@ -1533,7 +1532,7 @@ async def _remote_join(
             if too_complex is True:
                 raise SynapseError(
                     code=400,
-                    msg=self.hs.config.limit_remote_rooms.complexity_error,
+                    msg=self.hs.config.server.limit_remote_rooms.complexity_error,
                     errcode=Codes.RESOURCE_LIMIT_EXCEEDED,
                 )
 
@@ -1568,7 +1567,7 @@ async def _remote_join(
             )
             raise SynapseError(
                 code=400,
-                msg=self.hs.config.limit_remote_rooms.complexity_error,
+                msg=self.hs.config.server.limit_remote_rooms.complexity_error,
                 errcode=Codes.RESOURCE_LIMIT_EXCEEDED,
             )
 
diff --git a/synapse/handlers/saml.py b/synapse/handlers/saml.py
index 2fed9f377..727d75a50 100644
--- a/synapse/handlers/saml.py
+++ b/synapse/handlers/saml.py
@@ -22,7 +22,6 @@
 
 from synapse.api.errors import SynapseError
 from synapse.config import ConfigError
-from synapse.handlers._base import BaseHandler
 from synapse.handlers.sso import MappingException, UserAttributes
 from synapse.http.servlet import parse_string
 from synapse.http.site import SynapseRequest
@@ -51,9 +50,11 @@ class Saml2SessionData:
     ui_auth_session_id: Optional[str] = None
 
 
-class SamlHandler(BaseHandler):
+class SamlHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self.server_name = hs.hostname
         self._saml_client = Saml2Client(hs.config.saml2.saml2_sp_config)
         self._saml_idp_entityid = hs.config.saml2.saml2_idp_entityid
 
diff --git a/synapse/handlers/search.py b/synapse/handlers/search.py
index 8226d6f5a..a3ffa26be 100644
--- a/synapse/handlers/search.py
+++ b/synapse/handlers/search.py
@@ -26,17 +26,18 @@
 from synapse.types import JsonDict, UserID
 from synapse.visibility import filter_events_for_client
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class SearchHandler(BaseHandler):
+class SearchHandler:
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
+        self.state_handler = hs.get_state_handler()
+        self.clock = hs.get_clock()
+        self.hs = hs
         self._event_serializer = hs.get_event_client_serializer()
         self.storage = hs.get_storage()
         self.state_store = self.storage.state
@@ -105,7 +106,7 @@ async def search(
             dict to be returned to the client with results of search
         """
 
-        if not self.hs.config.enable_search:
+        if not self.hs.config.server.enable_search:
             raise SynapseError(400, "Search is disabled on this homeserver")
 
         batch_group = None
diff --git a/synapse/handlers/send_email.py b/synapse/handlers/send_email.py
index 25e6b012b..1a062a784 100644
--- a/synapse/handlers/send_email.py
+++ b/synapse/handlers/send_email.py
@@ -105,8 +105,13 @@ def build_sender_factory(**kwargs: Any) -> ESMTPSenderFactory:
         # set to enable TLS.
         factory = build_sender_factory(hostname=smtphost if enable_tls else None)
 
-    # the IReactorTCP interface claims host has to be a bytes, which seems to be wrong
-    reactor.connectTCP(smtphost, smtpport, factory, timeout=30, bindAddress=None)  # type: ignore[arg-type]
+    reactor.connectTCP(
+        smtphost,  # type: ignore[arg-type]
+        smtpport,
+        factory,
+        timeout=30,
+        bindAddress=None,
+    )
 
     await make_deferred_yieldable(d)
 
diff --git a/synapse/handlers/set_password.py b/synapse/handlers/set_password.py
index 56207c705..c57d08164 100644
--- a/synapse/handlers/set_password.py
+++ b/synapse/handlers/set_password.py
@@ -18,19 +18,17 @@
 from synapse.api.errors import Codes, StoreError, SynapseError
 from synapse.types import Requester
 
-from ._base import BaseHandler
-
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-class SetPasswordHandler(BaseHandler):
+class SetPasswordHandler:
     """Handler which deals with changing user account passwords"""
 
     def __init__(self, hs: "HomeServer"):
-        super().__init__(hs)
+        self.store = hs.get_datastore()
         self._auth_handler = hs.get_auth_handler()
         self._device_handler = hs.get_device_handler()
 
diff --git a/synapse/handlers/ui_auth/checkers.py b/synapse/handlers/ui_auth/checkers.py
index 8f5d465fa..184730ebe 100644
--- a/synapse/handlers/ui_auth/checkers.py
+++ b/synapse/handlers/ui_auth/checkers.py
@@ -153,21 +153,23 @@ async def _check_threepid(self, medium: str, authdict: dict) -> dict:
 
         # msisdns are currently always ThreepidBehaviour.REMOTE
         if medium == "msisdn":
-            if not self.hs.config.account_threepid_delegate_msisdn:
+            if not self.hs.config.registration.account_threepid_delegate_msisdn:
                 raise SynapseError(
                     400, "Phone number verification is not enabled on this homeserver"
                 )
             threepid = await identity_handler.threepid_from_creds(
-                self.hs.config.account_threepid_delegate_msisdn, threepid_creds
+                self.hs.config.registration.account_threepid_delegate_msisdn,
+                threepid_creds,
             )
         elif medium == "email":
             if (
                 self.hs.config.email.threepid_behaviour_email
                 == ThreepidBehaviour.REMOTE
             ):
-                assert self.hs.config.account_threepid_delegate_email
+                assert self.hs.config.registration.account_threepid_delegate_email
                 threepid = await identity_handler.threepid_from_creds(
-                    self.hs.config.account_threepid_delegate_email, threepid_creds
+                    self.hs.config.registration.account_threepid_delegate_email,
+                    threepid_creds,
                 )
             elif (
                 self.hs.config.email.threepid_behaviour_email == ThreepidBehaviour.LOCAL
@@ -240,7 +242,7 @@ def __init__(self, hs: "HomeServer"):
         _BaseThreepidAuthChecker.__init__(self, hs)
 
     def is_enabled(self) -> bool:
-        return bool(self.hs.config.account_threepid_delegate_msisdn)
+        return bool(self.hs.config.registration.account_threepid_delegate_msisdn)
 
     async def check_auth(self, authdict: dict, clientip: str) -> Any:
         return await self._check_threepid("msisdn", authdict)
@@ -252,7 +254,7 @@ class RegistrationTokenAuthChecker(UserInteractiveAuthChecker):
     def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.hs = hs
-        self._enabled = bool(hs.config.registration_requires_token)
+        self._enabled = bool(hs.config.registration.registration_requires_token)
         self.store = hs.get_datastore()
 
     def is_enabled(self) -> bool:
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index b91e7cb50..8810f048b 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -60,7 +60,7 @@ def __init__(self, hs: "HomeServer"):
         self.clock = hs.get_clock()
         self.notifier = hs.get_notifier()
         self.is_mine_id = hs.is_mine_id
-        self.update_user_directory = hs.config.update_user_directory
+        self.update_user_directory = hs.config.server.update_user_directory
         self.search_all_users = hs.config.userdirectory.user_directory_search_all_users
         self.spam_checker = hs.get_spam_checker()
         # The current position in the current_state_delta stream
@@ -132,12 +132,7 @@ async def handle_local_profile_change(
         # FIXME(#3714): We should probably do this in the same worker as all
         # the other changes.
 
-        # Support users are for diagnostics and should not appear in the user directory.
-        is_support = await self.store.is_support_user(user_id)
-        # When change profile information of deactivated user it should not appear in the user directory.
-        is_deactivated = await self.store.get_user_deactivated_status(user_id)
-
-        if not (is_support or is_deactivated):
+        if await self.store.should_include_local_user_in_dir(user_id):
             await self.store.update_profile_in_user_dir(
                 user_id, profile.display_name, profile.avatar_url
             )
@@ -208,6 +203,7 @@ async def _handle_deltas(self, deltas: List[Dict[str, Any]]) -> None:
                     public_value=Membership.JOIN,
                 )
 
+                is_remote = not self.is_mine_id(state_key)
                 if change is MatchChange.now_false:
                     # Need to check if the server left the room entirely, if so
                     # we might need to remove all the users in that room
@@ -225,32 +221,36 @@ async def _handle_deltas(self, deltas: List[Dict[str, Any]]) -> None:
 
                         for user_id in user_ids:
                             await self._handle_remove_user(room_id, user_id)
-                        return
+                        continue
                     else:
                         logger.debug("Server is still in room: %r", room_id)
 
-                is_support = await self.store.is_support_user(state_key)
-                if not is_support:
+                include_in_dir = (
+                    is_remote
+                    or await self.store.should_include_local_user_in_dir(state_key)
+                )
+                if include_in_dir:
                     if change is MatchChange.no_change:
-                        # Handle any profile changes
-                        await self._handle_profile_change(
-                            state_key, room_id, prev_event_id, event_id
-                        )
+                        # Handle any profile changes for remote users.
+                        # (For local users we are not forced to scan membership
+                        # events; instead the rest of the application calls
+                        # `handle_local_profile_change`.)
+                        if is_remote:
+                            await self._handle_profile_change(
+                                state_key, room_id, prev_event_id, event_id
+                            )
                         continue
 
                     if change is MatchChange.now_true:  # The user joined
-                        event = await self.store.get_event(event_id, allow_none=True)
-                        # It isn't expected for this event to not exist, but we
-                        # don't want the entire background process to break.
-                        if event is None:
-                            continue
-
-                        profile = ProfileInfo(
-                            avatar_url=event.content.get("avatar_url"),
-                            display_name=event.content.get("displayname"),
-                        )
-
-                        await self._handle_new_user(room_id, state_key, profile)
+                        # This may be the first time we've seen a remote user. If
+                        # so, ensure we have a directory entry for them. (We don't
+                        # need to do this for local users: their directory entry
+                        # is created at the point of registration.
+                        if is_remote:
+                            await self._upsert_directory_entry_for_remote_user(
+                                state_key, event_id
+                            )
+                        await self._track_user_joined_room(room_id, state_key)
                     else:  # The user left
                         await self._handle_remove_user(room_id, state_key)
             else:
@@ -300,7 +300,7 @@ async def _handle_room_publicity_change(
             room_id
         )
 
-        logger.debug("Change: %r, publicness: %r", publicness, is_public)
+        logger.debug("Publicness change: %r, is_public: %r", publicness, is_public)
 
         if publicness is MatchChange.now_true and not is_public:
             # If we became world readable but room isn't currently public then
@@ -311,42 +311,50 @@ async def _handle_room_publicity_change(
             # ignore the change
             return
 
-        other_users_in_room_with_profiles = (
-            await self.store.get_users_in_room_with_profiles(room_id)
-        )
+        users_in_room = await self.store.get_users_in_room(room_id)
 
         # Remove every user from the sharing tables for that room.
-        for user_id in other_users_in_room_with_profiles.keys():
+        for user_id in users_in_room:
             await self.store.remove_user_who_share_room(user_id, room_id)
 
         # Then, re-add them to the tables.
-        # NOTE: this is not the most efficient method, as handle_new_user sets
+        # NOTE: this is not the most efficient method, as _track_user_joined_room sets
         # up local_user -> other_user and other_user_whos_local -> local_user,
         # which when ran over an entire room, will result in the same values
         # being added multiple times. The batching upserts shouldn't make this
         # too bad, though.
-        for user_id, profile in other_users_in_room_with_profiles.items():
-            await self._handle_new_user(room_id, user_id, profile)
+        for user_id in users_in_room:
+            await self._track_user_joined_room(room_id, user_id)
 
-    async def _handle_new_user(
-        self, room_id: str, user_id: str, profile: ProfileInfo
+    async def _upsert_directory_entry_for_remote_user(
+        self, user_id: str, event_id: str
     ) -> None:
-        """Called when we might need to add user to directory
-
-        Args:
-            room_id: The room ID that user joined or started being public
-            user_id
+        """A remote user has just joined a room. Ensure they have an entry in
+        the user directory. The caller is responsible for making sure they're
+        remote.
         """
+        event = await self.store.get_event(event_id, allow_none=True)
+        # It isn't expected for this event to not exist, but we
+        # don't want the entire background process to break.
+        if event is None:
+            return
+
         logger.debug("Adding new user to dir, %r", user_id)
 
         await self.store.update_profile_in_user_dir(
-            user_id, profile.display_name, profile.avatar_url
+            user_id, event.content.get("displayname"), event.content.get("avatar_url")
         )
 
+    async def _track_user_joined_room(self, room_id: str, user_id: str) -> None:
+        """Someone's just joined a room. Update `users_in_public_rooms` or
+        `users_who_share_private_rooms` as appropriate.
+
+        The caller is responsible for ensuring that the given user is not excluded
+        from the user directory.
+        """
         is_public = await self.store.is_room_world_readable_or_publicly_joinable(
             room_id
         )
-        # Now we update users who share rooms with users.
         other_users_in_room = await self.store.get_users_in_room(room_id)
 
         if is_public:
@@ -356,13 +364,7 @@ async def _handle_new_user(
 
             # First, if they're our user then we need to update for every user
             if self.is_mine_id(user_id):
-
-                is_appservice = self.store.get_if_app_services_interested_in_user(
-                    user_id
-                )
-
-                # We don't care about appservice users.
-                if not is_appservice:
+                if await self.store.should_include_local_user_in_dir(user_id):
                     for other_user_id in other_users_in_room:
                         if user_id == other_user_id:
                             continue
@@ -374,10 +376,10 @@ async def _handle_new_user(
                 if user_id == other_user_id:
                     continue
 
-                is_appservice = self.store.get_if_app_services_interested_in_user(
+                include_other_user = self.is_mine_id(
                     other_user_id
-                )
-                if self.is_mine_id(other_user_id) and not is_appservice:
+                ) and await self.store.should_include_local_user_in_dir(other_user_id)
+                if include_other_user:
                     to_insert.add((other_user_id, user_id))
 
             if to_insert:
diff --git a/synapse/http/client.py b/synapse/http/client.py
index 5204c3d08..b5a2d333a 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -912,7 +912,7 @@ class InsecureInterceptableContextFactory(ssl.ContextFactory):
 
     def __init__(self):
         self._context = SSL.Context(SSL.SSLv23_METHOD)
-        self._context.set_verify(VERIFY_NONE, lambda *_: None)
+        self._context.set_verify(VERIFY_NONE, lambda *_: False)
 
     def getContext(self, hostname=None, port=None):
         return self._context
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index cdc36b8d2..4f5922468 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -327,23 +327,23 @@ def __init__(self, hs, tls_client_options_factory):
         self.reactor = hs.get_reactor()
 
         user_agent = hs.version_string
-        if hs.config.user_agent_suffix:
-            user_agent = "%s %s" % (user_agent, hs.config.user_agent_suffix)
+        if hs.config.server.user_agent_suffix:
+            user_agent = "%s %s" % (user_agent, hs.config.server.user_agent_suffix)
         user_agent = user_agent.encode("ascii")
 
         federation_agent = MatrixFederationAgent(
             self.reactor,
             tls_client_options_factory,
             user_agent,
-            hs.config.federation_ip_range_whitelist,
-            hs.config.federation_ip_range_blacklist,
+            hs.config.server.federation_ip_range_whitelist,
+            hs.config.server.federation_ip_range_blacklist,
         )
 
         # Use a BlacklistingAgentWrapper to prevent circumventing the IP
         # blacklist via IP literals in server names
         self.agent = BlacklistingAgentWrapper(
             federation_agent,
-            ip_blacklist=hs.config.federation_ip_range_blacklist,
+            ip_blacklist=hs.config.server.federation_ip_range_blacklist,
         )
 
         self.clock = hs.get_clock()
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 0df1bfbee..897ba5e45 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -563,7 +563,10 @@ def __init__(
 
         try:
             self._request.registerProducer(self, True)
-        except RuntimeError as e:
+        except AttributeError as e:
+            # Calling self._request.registerProducer might raise an AttributeError since
+            # the underlying Twisted code calls self._request.channel.registerProducer,
+            # however self._request.channel will be None if the connection was lost.
             logger.info("Connection disconnected before response was written: %r", e)
 
             # We drop our references to data we'll not use.
diff --git a/synapse/logging/_terse_json.py b/synapse/logging/_terse_json.py
index 6e82f7c7f..b78d6e17c 100644
--- a/synapse/logging/_terse_json.py
+++ b/synapse/logging/_terse_json.py
@@ -65,6 +65,12 @@ def _format(self, record: logging.LogRecord, event: dict) -> str:
             if key not in _IGNORED_LOG_RECORD_ATTRIBUTES:
                 event[key] = value
 
+        if record.exc_info:
+            exc_type, exc_value, _ = record.exc_info
+            if exc_type:
+                event["exc_type"] = f"{exc_type.__name__}"
+                event["exc_value"] = f"{exc_value}"
+
         return _encoder.encode(event)
 
 
diff --git a/synapse/logging/context.py b/synapse/logging/context.py
index 02e5ddd2e..bdc018774 100644
--- a/synapse/logging/context.py
+++ b/synapse/logging/context.py
@@ -52,7 +52,7 @@
 
     is_thread_resource_usage_supported = True
 
-    def get_thread_resource_usage() -> "Optional[resource._RUsage]":
+    def get_thread_resource_usage() -> "Optional[resource.struct_rusage]":
         return resource.getrusage(RUSAGE_THREAD)
 
 
@@ -61,7 +61,7 @@ def get_thread_resource_usage() -> "Optional[resource._RUsage]":
     # won't track resource usage.
     is_thread_resource_usage_supported = False
 
-    def get_thread_resource_usage() -> "Optional[resource._RUsage]":
+    def get_thread_resource_usage() -> "Optional[resource.struct_rusage]":
         return None
 
 
@@ -226,10 +226,10 @@ def __str__(self):
     def copy_to(self, record):
         pass
 
-    def start(self, rusage: "Optional[resource._RUsage]"):
+    def start(self, rusage: "Optional[resource.struct_rusage]"):
         pass
 
-    def stop(self, rusage: "Optional[resource._RUsage]"):
+    def stop(self, rusage: "Optional[resource.struct_rusage]"):
         pass
 
     def add_database_transaction(self, duration_sec):
@@ -289,7 +289,7 @@ def __init__(
 
         # The thread resource usage when the logcontext became active. None
         # if the context is not currently active.
-        self.usage_start: Optional[resource._RUsage] = None
+        self.usage_start: Optional[resource.struct_rusage] = None
 
         self.main_thread = get_thread_id()
         self.request = None
@@ -410,7 +410,7 @@ def copy_to(self, record) -> None:
         # we also track the current scope:
         record.scope = self.scope
 
-    def start(self, rusage: "Optional[resource._RUsage]") -> None:
+    def start(self, rusage: "Optional[resource.struct_rusage]") -> None:
         """
         Record that this logcontext is currently running.
 
@@ -435,7 +435,7 @@ def start(self, rusage: "Optional[resource._RUsage]") -> None:
         else:
             self.usage_start = rusage
 
-    def stop(self, rusage: "Optional[resource._RUsage]") -> None:
+    def stop(self, rusage: "Optional[resource.struct_rusage]") -> None:
         """
         Record that this logcontext is no longer running.
 
@@ -490,7 +490,7 @@ def get_resource_usage(self) -> ContextResourceUsage:
 
         return res
 
-    def _get_cputime(self, current: "resource._RUsage") -> Tuple[float, float]:
+    def _get_cputime(self, current: "resource.struct_rusage") -> Tuple[float, float]:
         """Get the cpu usage time between start() and the given rusage
 
         Args:
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index 03d2dd94f..20d23a426 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -339,6 +339,7 @@ def ensure_active_span_inner_2(*args, **kwargs):
                     "There was no active span when trying to %s."
                     " Did you forget to start one or did a context slip?",
                     message,
+                    stack_info=True,
                 )
 
                 return ret
@@ -806,6 +807,14 @@ def err_back(result):
                         result.addCallbacks(call_back, err_back)
 
                     else:
+                        if inspect.isawaitable(result):
+                            logger.error(
+                                "@trace may not have wrapped %s correctly! "
+                                "The function is not async but returned a %s.",
+                                func.__qualname__,
+                                type(result).__name__,
+                            )
+
                         scope.__exit__(None, None, None)
 
                     return result
diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index 3a1426075..2ab599a33 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -265,7 +265,7 @@ def __init__(self, name: str, instance_id: Optional[Union[int, str]] = None):
         super().__init__("%s-%s" % (name, instance_id))
         self._proc = _BackgroundProcess(name, self)
 
-    def start(self, rusage: "Optional[resource._RUsage]"):
+    def start(self, rusage: "Optional[resource.struct_rusage]"):
         """Log context has started running (again)."""
 
         super().start(rusage)
diff --git a/synapse/push/__init__.py b/synapse/push/__init__.py
index 2c23afe8e..820f6f3f7 100644
--- a/synapse/push/__init__.py
+++ b/synapse/push/__init__.py
@@ -94,7 +94,7 @@ def on_new_notifications(self, max_token: RoomStreamToken) -> None:
         self._start_processing()
 
     @abc.abstractmethod
-    def _start_processing(self):
+    def _start_processing(self) -> None:
         """Start processing push notifications."""
         raise NotImplementedError()
 
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index c337e530d..0622a37ae 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -290,6 +290,12 @@ def _condition_checker(
     return True
 
 
+MemberMap = Dict[str, Tuple[str, str]]
+Rule = Dict[str, dict]
+RulesByUser = Dict[str, List[Rule]]
+StateGroup = Union[object, int]
+
+
 @attr.s(slots=True)
 class RulesForRoomData:
     """The data stored in the cache by `RulesForRoom`.
@@ -299,16 +305,16 @@ class RulesForRoomData:
     """
 
     # event_id -> (user_id, state)
-    member_map = attr.ib(type=Dict[str, Tuple[str, str]], factory=dict)
+    member_map = attr.ib(type=MemberMap, factory=dict)
     # user_id -> rules
-    rules_by_user = attr.ib(type=Dict[str, List[Dict[str, dict]]], factory=dict)
+    rules_by_user = attr.ib(type=RulesByUser, factory=dict)
 
     # The last state group we updated the caches for. If the state_group of
     # a new event comes along, we know that we can just return the cached
     # result.
     # On invalidation of the rules themselves (if the user changes them),
     # we invalidate everything and set state_group to `object()`
-    state_group = attr.ib(type=Union[object, int], factory=object)
+    state_group = attr.ib(type=StateGroup, factory=object)
 
     # A sequence number to keep track of when we're allowed to update the
     # cache. We bump the sequence number when we invalidate the cache. If
@@ -532,7 +538,13 @@ async def _update_rules_with_member_event_ids(
 
         self.update_cache(sequence, members, ret_rules_by_user, state_group)
 
-    def update_cache(self, sequence, members, rules_by_user, state_group) -> None:
+    def update_cache(
+        self,
+        sequence: int,
+        members: MemberMap,
+        rules_by_user: RulesByUser,
+        state_group: StateGroup,
+    ) -> None:
         if sequence == self.data.sequence:
             self.data.member_map.update(members)
             self.data.rules_by_user = rules_by_user
diff --git a/synapse/push/clientformat.py b/synapse/push/clientformat.py
index 1fc9716a3..c5708cd88 100644
--- a/synapse/push/clientformat.py
+++ b/synapse/push/clientformat.py
@@ -19,7 +19,9 @@
 from synapse.types import UserID
 
 
-def format_push_rules_for_user(user: UserID, ruleslist) -> Dict[str, Dict[str, list]]:
+def format_push_rules_for_user(
+    user: UserID, ruleslist: List
+) -> Dict[str, Dict[str, list]]:
     """Converts a list of rawrules and a enabled map into nested dictionaries
     to match the Matrix client-server format for push rules"""
 
diff --git a/synapse/push/httppusher.py b/synapse/push/httppusher.py
index eac65572b..dbf4ad7f9 100644
--- a/synapse/push/httppusher.py
+++ b/synapse/push/httppusher.py
@@ -403,10 +403,10 @@ async def dispatch_push(
             rejected = resp["rejected"]
         return rejected
 
-    async def _send_badge(self, badge):
+    async def _send_badge(self, badge: int) -> None:
         """
         Args:
-            badge (int): number of unread messages
+            badge: number of unread messages
         """
         logger.debug("Sending updated badge count %d to %s", badge, self.name)
         d = {
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index e38e3c5d4..ce299ba3d 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -892,7 +892,7 @@ def safe_text(raw_text: str) -> jinja2.Markup:
         A Markup object ready to safely use in a Jinja template.
     """
     return jinja2.Markup(
-        bleach.linkify(bleach.clean(raw_text, tags=[], attributes={}, strip=False))
+        bleach.linkify(bleach.clean(raw_text, tags=[], attributes=[], strip=False))
     )
 
 
diff --git a/synapse/replication/http/_base.py b/synapse/replication/http/_base.py
index f1b78d09f..e047ec74d 100644
--- a/synapse/replication/http/_base.py
+++ b/synapse/replication/http/_base.py
@@ -182,85 +182,87 @@ def make_client(cls, hs):
             )
 
         @trace(opname="outgoing_replication_request")
-        @outgoing_gauge.track_inprogress()
         async def send_request(*, instance_name="master", **kwargs):
-            if instance_name == local_instance_name:
-                raise Exception("Trying to send HTTP request to self")
-            if instance_name == "master":
-                host = master_host
-                port = master_port
-            elif instance_name in instance_map:
-                host = instance_map[instance_name].host
-                port = instance_map[instance_name].port
-            else:
-                raise Exception(
-                    "Instance %r not in 'instance_map' config" % (instance_name,)
+            with outgoing_gauge.track_inprogress():
+                if instance_name == local_instance_name:
+                    raise Exception("Trying to send HTTP request to self")
+                if instance_name == "master":
+                    host = master_host
+                    port = master_port
+                elif instance_name in instance_map:
+                    host = instance_map[instance_name].host
+                    port = instance_map[instance_name].port
+                else:
+                    raise Exception(
+                        "Instance %r not in 'instance_map' config" % (instance_name,)
+                    )
+
+                data = await cls._serialize_payload(**kwargs)
+
+                url_args = [
+                    urllib.parse.quote(kwargs[name], safe="") for name in cls.PATH_ARGS
+                ]
+
+                if cls.CACHE:
+                    txn_id = random_string(10)
+                    url_args.append(txn_id)
+
+                if cls.METHOD == "POST":
+                    request_func = client.post_json_get_json
+                elif cls.METHOD == "PUT":
+                    request_func = client.put_json
+                elif cls.METHOD == "GET":
+                    request_func = client.get_json
+                else:
+                    # We have already asserted in the constructor that a
+                    # compatible was picked, but lets be paranoid.
+                    raise Exception(
+                        "Unknown METHOD on %s replication endpoint" % (cls.NAME,)
+                    )
+
+                uri = "http://%s:%s/_synapse/replication/%s/%s" % (
+                    host,
+                    port,
+                    cls.NAME,
+                    "/".join(url_args),
                 )
 
-            data = await cls._serialize_payload(**kwargs)
-
-            url_args = [
-                urllib.parse.quote(kwargs[name], safe="") for name in cls.PATH_ARGS
-            ]
-
-            if cls.CACHE:
-                txn_id = random_string(10)
-                url_args.append(txn_id)
-
-            if cls.METHOD == "POST":
-                request_func = client.post_json_get_json
-            elif cls.METHOD == "PUT":
-                request_func = client.put_json
-            elif cls.METHOD == "GET":
-                request_func = client.get_json
-            else:
-                # We have already asserted in the constructor that a
-                # compatible was picked, but lets be paranoid.
-                raise Exception(
-                    "Unknown METHOD on %s replication endpoint" % (cls.NAME,)
-                )
-
-            uri = "http://%s:%s/_synapse/replication/%s/%s" % (
-                host,
-                port,
-                cls.NAME,
-                "/".join(url_args),
-            )
-
-            try:
-                # We keep retrying the same request for timeouts. This is so that we
-                # have a good idea that the request has either succeeded or failed on
-                # the master, and so whether we should clean up or not.
-                while True:
-                    headers: Dict[bytes, List[bytes]] = {}
-                    # Add an authorization header, if configured.
-                    if replication_secret:
-                        headers[b"Authorization"] = [b"Bearer " + replication_secret]
-                    opentracing.inject_header_dict(headers, check_destination=False)
-                    try:
-                        result = await request_func(uri, data, headers=headers)
-                        break
-                    except RequestTimedOutError:
-                        if not cls.RETRY_ON_TIMEOUT:
-                            raise
-
-                    logger.warning("%s request timed out; retrying", cls.NAME)
-
-                    # If we timed out we probably don't need to worry about backing
-                    # off too much, but lets just wait a little anyway.
-                    await clock.sleep(1)
-            except HttpResponseException as e:
-                # We convert to SynapseError as we know that it was a SynapseError
-                # on the main process that we should send to the client. (And
-                # importantly, not stack traces everywhere)
-                _outgoing_request_counter.labels(cls.NAME, e.code).inc()
-                raise e.to_synapse_error()
-            except Exception as e:
-                _outgoing_request_counter.labels(cls.NAME, "ERR").inc()
-                raise SynapseError(502, "Failed to talk to main process") from e
-
-            _outgoing_request_counter.labels(cls.NAME, 200).inc()
-            return result
+                try:
+                    # We keep retrying the same request for timeouts. This is so that we
+                    # have a good idea that the request has either succeeded or failed
+                    # on the master, and so whether we should clean up or not.
+                    while True:
+                        headers: Dict[bytes, List[bytes]] = {}
+                        # Add an authorization header, if configured.
+                        if replication_secret:
+                            headers[b"Authorization"] = [
+                                b"Bearer " + replication_secret
+                            ]
+                        opentracing.inject_header_dict(headers, check_destination=False)
+                        try:
+                            result = await request_func(uri, data, headers=headers)
+                            break
+                        except RequestTimedOutError:
+                            if not cls.RETRY_ON_TIMEOUT:
+                                raise
+
+                        logger.warning("%s request timed out; retrying", cls.NAME)
+
+                        # If we timed out we probably don't need to worry about backing
+                        # off too much, but lets just wait a little anyway.
+                        await clock.sleep(1)
+                except HttpResponseException as e:
+                    # We convert to SynapseError as we know that it was a SynapseError
+                    # on the main process that we should send to the client. (And
+                    # importantly, not stack traces everywhere)
+                    _outgoing_request_counter.labels(cls.NAME, e.code).inc()
+                    raise e.to_synapse_error()
+                except Exception as e:
+                    _outgoing_request_counter.labels(cls.NAME, "ERR").inc()
+                    raise SynapseError(502, "Failed to talk to main process") from e
+
+                _outgoing_request_counter.labels(cls.NAME, 200).inc()
+                return result
 
         return send_request
 
diff --git a/synapse/replication/slave/storage/_slaved_id_tracker.py b/synapse/replication/slave/storage/_slaved_id_tracker.py
index 2cb748904..8c1bf9227 100644
--- a/synapse/replication/slave/storage/_slaved_id_tracker.py
+++ b/synapse/replication/slave/storage/_slaved_id_tracker.py
@@ -13,14 +13,14 @@
 # limitations under the License.
 from typing import List, Optional, Tuple
 
-from synapse.storage.types import Connection
+from synapse.storage.database import LoggingDatabaseConnection
 from synapse.storage.util.id_generators import _load_current_id
 
 
 class SlavedIdTracker:
     def __init__(
         self,
-        db_conn: Connection,
+        db_conn: LoggingDatabaseConnection,
         table: str,
         column: str,
         extra_tables: Optional[List[Tuple[str, str]]] = None,
diff --git a/synapse/replication/slave/storage/pushers.py b/synapse/replication/slave/storage/pushers.py
index 2672a2c94..cea90c0f1 100644
--- a/synapse/replication/slave/storage/pushers.py
+++ b/synapse/replication/slave/storage/pushers.py
@@ -15,9 +15,8 @@
 from typing import TYPE_CHECKING
 
 from synapse.replication.tcp.streams import PushersStream
-from synapse.storage.database import DatabasePool
+from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
 from synapse.storage.databases.main.pusher import PusherWorkerStore
-from synapse.storage.types import Connection
 
 from ._base import BaseSlavedStore
 from ._slaved_id_tracker import SlavedIdTracker
@@ -27,7 +26,12 @@
 
 
 class SlavedPusherStore(PusherWorkerStore, BaseSlavedStore):
-    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ):
         super().__init__(database, db_conn, hs)
         self._pushers_id_gen = SlavedIdTracker(  # type: ignore
             db_conn, "pushers", "id", extra_tables=[("deleted_pushers", "stream_id")]
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 37769ace4..961c17762 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -117,7 +117,7 @@ def __init__(self, hs: "HomeServer"):
         self._instance_name = hs.get_instance_name()
         self._typing_handler = hs.get_typing_handler()
 
-        self._notify_pushers = hs.config.start_pushers
+        self._notify_pushers = hs.config.worker.start_pushers
         self._pusher_pool = hs.get_pusherpool()
         self._presence_handler = hs.get_presence_handler()
 
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index 1438a82b6..6aa931802 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -171,7 +171,10 @@ def __init__(self, hs: "HomeServer"):
             if hs.config.worker.worker_app is not None:
                 continue
 
-            if stream.NAME == FederationStream.NAME and hs.config.send_federation:
+            if (
+                stream.NAME == FederationStream.NAME
+                and hs.config.worker.send_federation
+            ):
                 # We only support federation stream if federation sending
                 # has been disabled on the master.
                 continue
@@ -225,7 +228,7 @@ def __init__(self, hs: "HomeServer"):
         self._is_master = hs.config.worker.worker_app is None
 
         self._federation_sender = None
-        if self._is_master and not hs.config.send_federation:
+        if self._is_master and not hs.config.worker.send_federation:
             self._federation_sender = hs.get_federation_sender()
 
         self._server_notices_sender = None
@@ -315,7 +318,7 @@ def start_replication(self, hs):
                 hs, outbound_redis_connection
             )
             hs.get_reactor().connectTCP(
-                hs.config.redis.redis_host.encode(),
+                hs.config.redis.redis_host,  # type: ignore[arg-type]
                 hs.config.redis.redis_port,
                 self._factory,
             )
@@ -324,7 +327,11 @@ def start_replication(self, hs):
             self._factory = DirectTcpReplicationClientFactory(hs, client_name, self)
             host = hs.config.worker.worker_replication_host
             port = hs.config.worker.worker_replication_port
-            hs.get_reactor().connectTCP(host.encode(), port, self._factory)
+            hs.get_reactor().connectTCP(
+                host,  # type: ignore[arg-type]
+                port,
+                self._factory,
+            )
 
     def get_streams(self) -> Dict[str, Stream]:
         """Get a map from stream name to all streams."""
diff --git a/synapse/replication/tcp/redis.py b/synapse/replication/tcp/redis.py
index 8c0df627c..062fe2f33 100644
--- a/synapse/replication/tcp/redis.py
+++ b/synapse/replication/tcp/redis.py
@@ -364,6 +364,12 @@ def lazyConnection(
     factory.continueTrying = reconnect
 
     reactor = hs.get_reactor()
-    reactor.connectTCP(host.encode(), port, factory, timeout=30, bindAddress=None)
+    reactor.connectTCP(
+        host,  # type: ignore[arg-type]
+        port,
+        factory,
+        timeout=30,
+        bindAddress=None,
+    )
 
     return factory.handler
diff --git a/synapse/replication/tcp/resource.py b/synapse/replication/tcp/resource.py
index 030852cb5..80f9b23bf 100644
--- a/synapse/replication/tcp/resource.py
+++ b/synapse/replication/tcp/resource.py
@@ -71,7 +71,7 @@ def __init__(self, hs):
         self.notifier = hs.get_notifier()
         self._instance_name = hs.get_instance_name()
 
-        self._replication_torture_level = hs.config.replication_torture_level
+        self._replication_torture_level = hs.config.server.replication_torture_level
 
         self.notifier.add_replication_callback(self.on_notifier_poke)
 
diff --git a/synapse/rest/admin/users.py b/synapse/rest/admin/users.py
index 46bfec462..f20aa6530 100644
--- a/synapse/rest/admin/users.py
+++ b/synapse/rest/admin/users.py
@@ -442,7 +442,7 @@ def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
     async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         self._clear_old_nonces()
 
-        if not self.hs.config.registration_shared_secret:
+        if not self.hs.config.registration.registration_shared_secret:
             raise SynapseError(400, "Shared secret registration is not enabled")
 
         body = parse_json_object_from_request(request)
@@ -498,7 +498,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         got_mac = body["mac"]
 
         want_mac_builder = hmac.new(
-            key=self.hs.config.registration_shared_secret.encode(),
+            key=self.hs.config.registration.registration_shared_secret.encode(),
             digestmod=hashlib.sha1,
         )
         want_mac_builder.update(nonce.encode("utf8"))
diff --git a/synapse/rest/client/account.py b/synapse/rest/client/account.py
index 0d3d33dba..466d528ce 100644
--- a/synapse/rest/client/account.py
+++ b/synapse/rest/client/account.py
@@ -120,7 +120,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         )
 
         if existing_user_id is None:
-            if self.config.request_token_inhibit_3pid_errors:
+            if self.config.server.request_token_inhibit_3pid_errors:
                 # Make the client think the operation succeeded. See the rationale in the
                 # comments for request_token_inhibit_3pid_errors.
                 # Also wait for some random amount of time between 100ms and 1s to make it
@@ -131,11 +131,11 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             raise SynapseError(400, "Email not found", Codes.THREEPID_NOT_FOUND)
 
         if self.config.email.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
-            assert self.hs.config.account_threepid_delegate_email
+            assert self.hs.config.registration.account_threepid_delegate_email
 
             # Have the configured identity server handle the request
             ret = await self.identity_handler.requestEmailToken(
-                self.hs.config.account_threepid_delegate_email,
+                self.hs.config.registration.account_threepid_delegate_email,
                 email,
                 client_secret,
                 send_attempt,
@@ -412,7 +412,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         existing_user_id = await self.store.get_user_id_by_threepid("email", email)
 
         if existing_user_id is not None:
-            if self.config.request_token_inhibit_3pid_errors:
+            if self.config.server.request_token_inhibit_3pid_errors:
                 # Make the client think the operation succeeded. See the rationale in the
                 # comments for request_token_inhibit_3pid_errors.
                 # Also wait for some random amount of time between 100ms and 1s to make it
@@ -423,11 +423,11 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             raise SynapseError(400, "Email is already in use", Codes.THREEPID_IN_USE)
 
         if self.config.email.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
-            assert self.hs.config.account_threepid_delegate_email
+            assert self.hs.config.registration.account_threepid_delegate_email
 
             # Have the configured identity server handle the request
             ret = await self.identity_handler.requestEmailToken(
-                self.hs.config.account_threepid_delegate_email,
+                self.hs.config.registration.account_threepid_delegate_email,
                 email,
                 client_secret,
                 send_attempt,
@@ -495,7 +495,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         existing_user_id = await self.store.get_user_id_by_threepid("msisdn", msisdn)
 
         if existing_user_id is not None:
-            if self.hs.config.request_token_inhibit_3pid_errors:
+            if self.hs.config.server.request_token_inhibit_3pid_errors:
                 # Make the client think the operation succeeded. See the rationale in the
                 # comments for request_token_inhibit_3pid_errors.
                 # Also wait for some random amount of time between 100ms and 1s to make it
@@ -505,7 +505,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
 
             raise SynapseError(400, "MSISDN is already in use", Codes.THREEPID_IN_USE)
 
-        if not self.hs.config.account_threepid_delegate_msisdn:
+        if not self.hs.config.registration.account_threepid_delegate_msisdn:
             logger.warning(
                 "No upstream msisdn account_threepid_delegate configured on the server to "
                 "handle this request"
@@ -516,7 +516,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             )
 
         ret = await self.identity_handler.requestMsisdnToken(
-            self.hs.config.account_threepid_delegate_msisdn,
+            self.hs.config.registration.account_threepid_delegate_msisdn,
             country,
             phone_number,
             client_secret,
@@ -613,7 +613,7 @@ def __init__(self, hs: "HomeServer"):
         self.identity_handler = hs.get_identity_handler()
 
     async def on_POST(self, request: Request) -> Tuple[int, JsonDict]:
-        if not self.config.account_threepid_delegate_msisdn:
+        if not self.config.registration.account_threepid_delegate_msisdn:
             raise SynapseError(
                 400,
                 "This homeserver is not validating phone numbers. Use an identity server "
@@ -626,7 +626,7 @@ async def on_POST(self, request: Request) -> Tuple[int, JsonDict]:
 
         # Proxy submit_token request to msisdn threepid delegate
         response = await self.identity_handler.proxy_msisdn_submit_token(
-            self.config.account_threepid_delegate_msisdn,
+            self.config.registration.account_threepid_delegate_msisdn,
             body["client_secret"],
             body["sid"],
             body["token"],
@@ -653,7 +653,7 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         return 200, {"threepids": threepids}
 
     async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        if not self.hs.config.enable_3pid_changes:
+        if not self.hs.config.registration.enable_3pid_changes:
             raise SynapseError(
                 400, "3PID changes are disabled on this server", Codes.FORBIDDEN
             )
@@ -703,7 +703,7 @@ def __init__(self, hs: "HomeServer"):
 
     @interactive_auth_handler
     async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        if not self.hs.config.enable_3pid_changes:
+        if not self.hs.config.registration.enable_3pid_changes:
             raise SynapseError(
                 400, "3PID changes are disabled on this server", Codes.FORBIDDEN
             )
@@ -811,7 +811,7 @@ def __init__(self, hs: "HomeServer"):
         self.auth_handler = hs.get_auth_handler()
 
     async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        if not self.hs.config.enable_3pid_changes:
+        if not self.hs.config.registration.enable_3pid_changes:
             raise SynapseError(
                 400, "3PID changes are disabled on this server", Codes.FORBIDDEN
             )
@@ -924,8 +924,8 @@ def assert_valid_next_link(hs: "HomeServer", next_link: str) -> None:
     # If the domain whitelist is set, the domain must be in it
     if (
         valid
-        and hs.config.next_link_domain_whitelist is not None
-        and next_link_parsed.hostname not in hs.config.next_link_domain_whitelist
+        and hs.config.server.next_link_domain_whitelist is not None
+        and next_link_parsed.hostname not in hs.config.server.next_link_domain_whitelist
     ):
         valid = False
 
@@ -945,9 +945,13 @@ def __init__(self, hs: "HomeServer"):
         self.auth = hs.get_auth()
 
     async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        requester = await self.auth.get_user_by_req(request)
+        requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
-        response = {"user_id": requester.user.to_string()}
+        response = {
+            "user_id": requester.user.to_string(),
+            # MSC: https://github.com/matrix-org/matrix-doc/pull/3069
+            "org.matrix.msc3069.is_guest": bool(requester.is_guest),
+        }
 
         # Appservices and similar accounts do not have device IDs
         # that we can report on, so exclude them for compliance.
diff --git a/synapse/rest/client/auth.py b/synapse/rest/client/auth.py
index 282861fae..9c15a0433 100644
--- a/synapse/rest/client/auth.py
+++ b/synapse/rest/client/auth.py
@@ -48,9 +48,11 @@ def __init__(self, hs: "HomeServer"):
         self.auth_handler = hs.get_auth_handler()
         self.registration_handler = hs.get_registration_handler()
         self.recaptcha_template = hs.config.captcha.recaptcha_template
-        self.terms_template = hs.config.terms_template
-        self.registration_token_template = hs.config.registration_token_template
-        self.success_template = hs.config.fallback_success_template
+        self.terms_template = hs.config.consent.terms_template
+        self.registration_token_template = (
+            hs.config.registration.registration_token_template
+        )
+        self.success_template = hs.config.registration.fallback_success_template
 
     async def on_GET(self, request: SynapseRequest, stagetype: str) -> None:
         session = parse_string(request, "session")
diff --git a/synapse/rest/client/capabilities.py b/synapse/rest/client/capabilities.py
index 65b3b5ce2..2a3e24ae7 100644
--- a/synapse/rest/client/capabilities.py
+++ b/synapse/rest/client/capabilities.py
@@ -44,10 +44,10 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         await self.auth.get_user_by_req(request, allow_guest=True)
         change_password = self.auth_handler.can_change_password()
 
-        response = {
+        response: JsonDict = {
             "capabilities": {
                 "m.room_versions": {
-                    "default": self.config.default_room_version.identifier,
+                    "default": self.config.server.default_room_version.identifier,
                     "available": {
                         v.identifier: v.disposition
                         for v in KNOWN_ROOM_VERSIONS.values()
@@ -64,13 +64,13 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
 
         if self.config.experimental.msc3283_enabled:
             response["capabilities"]["org.matrix.msc3283.set_displayname"] = {
-                "enabled": self.config.enable_set_displayname
+                "enabled": self.config.registration.enable_set_displayname
             }
             response["capabilities"]["org.matrix.msc3283.set_avatar_url"] = {
-                "enabled": self.config.enable_set_avatar_url
+                "enabled": self.config.registration.enable_set_avatar_url
             }
             response["capabilities"]["org.matrix.msc3283.3pid_changes"] = {
-                "enabled": self.config.enable_3pid_changes
+                "enabled": self.config.registration.enable_3pid_changes
             }
 
         return 200, response
diff --git a/synapse/rest/client/filter.py b/synapse/rest/client/filter.py
index 6ed60c741..cc1c2f973 100644
--- a/synapse/rest/client/filter.py
+++ b/synapse/rest/client/filter.py
@@ -90,7 +90,7 @@ async def on_POST(
             raise AuthError(403, "Can only create filters for local users")
 
         content = parse_json_object_from_request(request)
-        set_timeline_upper_limit(content, self.hs.config.filter_timeline_limit)
+        set_timeline_upper_limit(content, self.hs.config.server.filter_timeline_limit)
 
         filter_id = await self.filtering.add_user_filter(
             user_localpart=target_user.localpart, user_filter=content
diff --git a/synapse/rest/client/login.py b/synapse/rest/client/login.py
index fa5c173f4..d49a647b0 100644
--- a/synapse/rest/client/login.py
+++ b/synapse/rest/client/login.py
@@ -79,7 +79,7 @@ def __init__(self, hs: "HomeServer"):
         self.saml2_enabled = hs.config.saml2.saml2_enabled
         self.cas_enabled = hs.config.cas.cas_enabled
         self.oidc_enabled = hs.config.oidc.oidc_enabled
-        self._msc2918_enabled = hs.config.access_token_lifetime is not None
+        self._msc2918_enabled = hs.config.registration.access_token_lifetime is not None
 
         self.auth = hs.get_auth()
 
@@ -447,7 +447,7 @@ class RefreshTokenServlet(RestServlet):
     def __init__(self, hs: "HomeServer"):
         self._auth_handler = hs.get_auth_handler()
         self._clock = hs.get_clock()
-        self.access_token_lifetime = hs.config.access_token_lifetime
+        self.access_token_lifetime = hs.config.registration.access_token_lifetime
 
     async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         refresh_submission = parse_json_object_from_request(request)
@@ -556,7 +556,7 @@ async def on_GET(self, request: SynapseRequest) -> None:
 
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     LoginRestServlet(hs).register(http_server)
-    if hs.config.access_token_lifetime is not None:
+    if hs.config.registration.access_token_lifetime is not None:
         RefreshTokenServlet(hs).register(http_server)
     SsoRedirectServlet(hs).register(http_server)
     if hs.config.cas.cas_enabled:
diff --git a/synapse/rest/client/profile.py b/synapse/rest/client/profile.py
index daf8760dc..1eb09b958 100644
--- a/synapse/rest/client/profile.py
+++ b/synapse/rest/client/profile.py
@@ -41,7 +41,7 @@ async def on_GET(
     ) -> Tuple[int, JsonDict]:
         requester_user = None
 
-        if self.hs.config.require_auth_for_profile_requests:
+        if self.hs.config.server.require_auth_for_profile_requests:
             requester = await self.auth.get_user_by_req(request)
             requester_user = requester.user
 
@@ -97,7 +97,7 @@ async def on_GET(
     ) -> Tuple[int, JsonDict]:
         requester_user = None
 
-        if self.hs.config.require_auth_for_profile_requests:
+        if self.hs.config.server.require_auth_for_profile_requests:
             requester = await self.auth.get_user_by_req(request)
             requester_user = requester.user
 
@@ -152,7 +152,7 @@ async def on_GET(
     ) -> Tuple[int, JsonDict]:
         requester_user = None
 
-        if self.hs.config.require_auth_for_profile_requests:
+        if self.hs.config.server.require_auth_for_profile_requests:
             requester = await self.auth.get_user_by_req(request)
             requester_user = requester.user
 
diff --git a/synapse/rest/client/push_rule.py b/synapse/rest/client/push_rule.py
index ecebc46e8..6f796d5e5 100644
--- a/synapse/rest/client/push_rule.py
+++ b/synapse/rest/client/push_rule.py
@@ -61,7 +61,9 @@ def __init__(self, hs: "HomeServer"):
         self.notifier = hs.get_notifier()
         self._is_worker = hs.config.worker.worker_app is not None
 
-        self._users_new_default_push_rules = hs.config.users_new_default_push_rules
+        self._users_new_default_push_rules = (
+            hs.config.server.users_new_default_push_rules
+        )
 
     async def on_PUT(self, request: SynapseRequest, path: str) -> Tuple[int, JsonDict]:
         if self._is_worker:
diff --git a/synapse/rest/client/register.py b/synapse/rest/client/register.py
index 9b6f7f8d4..195e51cf1 100644
--- a/synapse/rest/client/register.py
+++ b/synapse/rest/client/register.py
@@ -130,7 +130,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         )
 
         if existing_user_id is not None:
-            if self.hs.config.request_token_inhibit_3pid_errors:
+            if self.hs.config.server.request_token_inhibit_3pid_errors:
                 # Make the client think the operation succeeded. See the rationale in the
                 # comments for request_token_inhibit_3pid_errors.
                 # Also wait for some random amount of time between 100ms and 1s to make it
@@ -141,11 +141,11 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             raise SynapseError(400, "Email is already in use", Codes.THREEPID_IN_USE)
 
         if self.config.email.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
-            assert self.hs.config.account_threepid_delegate_email
+            assert self.hs.config.registration.account_threepid_delegate_email
 
             # Have the configured identity server handle the request
             ret = await self.identity_handler.requestEmailToken(
-                self.hs.config.account_threepid_delegate_email,
+                self.hs.config.registration.account_threepid_delegate_email,
                 email,
                 client_secret,
                 send_attempt,
@@ -212,7 +212,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         )
 
         if existing_user_id is not None:
-            if self.hs.config.request_token_inhibit_3pid_errors:
+            if self.hs.config.server.request_token_inhibit_3pid_errors:
                 # Make the client think the operation succeeded. See the rationale in the
                 # comments for request_token_inhibit_3pid_errors.
                 # Also wait for some random amount of time between 100ms and 1s to make it
@@ -224,7 +224,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                 400, "Phone number is already in use", Codes.THREEPID_IN_USE
             )
 
-        if not self.hs.config.account_threepid_delegate_msisdn:
+        if not self.hs.config.registration.account_threepid_delegate_msisdn:
             logger.warning(
                 "No upstream msisdn account_threepid_delegate configured on the server to "
                 "handle this request"
@@ -234,7 +234,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             )
 
         ret = await self.identity_handler.requestMsisdnToken(
-            self.hs.config.account_threepid_delegate_msisdn,
+            self.hs.config.registration.account_threepid_delegate_msisdn,
             country,
             phone_number,
             client_secret,
@@ -344,7 +344,7 @@ def __init__(self, hs: "HomeServer"):
         )
 
     async def on_GET(self, request: Request) -> Tuple[int, JsonDict]:
-        if not self.hs.config.enable_registration:
+        if not self.hs.config.registration.enable_registration:
             raise SynapseError(
                 403, "Registration has been disabled", errcode=Codes.FORBIDDEN
             )
@@ -388,7 +388,7 @@ def __init__(self, hs: "HomeServer"):
     async def on_GET(self, request: Request) -> Tuple[int, JsonDict]:
         await self.ratelimiter.ratelimit(None, (request.getClientIP(),))
 
-        if not self.hs.config.enable_registration:
+        if not self.hs.config.registration.enable_registration:
             raise SynapseError(
                 403, "Registration has been disabled", errcode=Codes.FORBIDDEN
             )
@@ -416,8 +416,8 @@ def __init__(self, hs: "HomeServer"):
         self.ratelimiter = hs.get_registration_ratelimiter()
         self.password_policy_handler = hs.get_password_policy_handler()
         self.clock = hs.get_clock()
-        self._registration_enabled = self.hs.config.enable_registration
-        self._msc2918_enabled = hs.config.access_token_lifetime is not None
+        self._registration_enabled = self.hs.config.registration.enable_registration
+        self._msc2918_enabled = hs.config.registration.access_token_lifetime is not None
 
         self._registration_flows = _calculate_registration_flows(
             hs.config, self.auth_handler
@@ -607,7 +607,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                             400, "%s is already in use" % medium, Codes.THREEPID_IN_USE
                         )
 
-        if self.hs.config.register_mxid_from_3pid:
+        if self.hs.config.registration.register_mxid_from_3pid:
             # override the desired_username based on the 3PID if any.
             # reset it first to avoid folks picking their own username.
             desired_username = None
@@ -618,7 +618,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             # desired_username
             if auth_result:
                 if (
-                    self.hs.config.register_mxid_from_3pid == "email"
+                    self.hs.config.registration.register_mxid_from_3pid == "email"
                     and LoginType.EMAIL_IDENTITY in auth_result
                 ):
                     address = auth_result[LoginType.EMAIL_IDENTITY]["address"]
@@ -656,7 +656,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                         # Custom mapping between email address and display name
                         desired_display_name = _map_email_to_displayname(address)
                 elif (
-                    self.hs.config.register_mxid_from_3pid == "msisdn"
+                    self.hs.config.registration.register_mxid_from_3pid == "msisdn"
                     and LoginType.MSISDN in auth_result
                 ):
                     desired_username = auth_result[LoginType.MSISDN]["address"]
@@ -686,7 +686,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             if not password_hash:
                 raise SynapseError(400, "Missing params: password", Codes.MISSING_PARAM)
 
-            if not self.hs.config.register_mxid_from_3pid:
+            if not self.hs.config.registration.register_mxid_from_3pid:
                 desired_username = params.get("username", None)
             else:
                 # we keep the original desired_username derived from the 3pid above
@@ -749,7 +749,7 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             # written to the db
             if threepid:
                 if is_threepid_reserved(
-                    self.hs.config.mau_limits_reserved_threepids, threepid
+                    self.hs.config.server.mau_limits_reserved_threepids, threepid
                 ):
                     await self.store.upsert_monthly_active_user(registered_user_id)
 
@@ -867,7 +867,7 @@ async def _create_registration_details(
     async def _do_guest_registration(
         self, params: JsonDict, address: Optional[str] = None
     ) -> Tuple[int, JsonDict]:
-        if not self.hs.config.allow_guest_access:
+        if not self.hs.config.registration.allow_guest_access:
             raise SynapseError(403, "Guest access is disabled")
         user_id = await self.registration_handler.register_user(
             make_guest=True, address=address
@@ -970,13 +970,13 @@ def _calculate_registration_flows(
     """
     # FIXME: need a better error than "no auth flow found" for scenarios
     # where we required 3PID for registration but the user didn't give one
-    require_email = "email" in config.registrations_require_3pid
-    require_msisdn = "msisdn" in config.registrations_require_3pid
+    require_email = "email" in config.registration.registrations_require_3pid
+    require_msisdn = "msisdn" in config.registration.registrations_require_3pid
 
     show_msisdn = True
     show_email = True
 
-    if config.disable_msisdn_registration:
+    if config.registration.disable_msisdn_registration:
         show_msisdn = False
         require_msisdn = False
 
@@ -1030,7 +1030,7 @@ def _calculate_registration_flows(
             flow.insert(0, LoginType.RECAPTCHA)
 
     # Prepend registration token to all flows if we're requiring a token
-    if config.registration_requires_token:
+    if config.registration.registration_requires_token:
         for flow in flows:
             flow.insert(0, LoginType.REGISTRATION_TOKEN)
 
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index f5c5be317..9f266fdae 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -369,7 +369,7 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             # Option to allow servers to require auth when accessing
             # /publicRooms via CS API. This is especially helpful in private
             # federations.
-            if not self.hs.config.allow_public_rooms_without_auth:
+            if not self.hs.config.server.allow_public_rooms_without_auth:
                 raise
 
             # We allow people to not be authed if they're just looking at our
diff --git a/synapse/rest/client/room_batch.py b/synapse/rest/client/room_batch.py
index bf14ec384..38ad4c244 100644
--- a/synapse/rest/client/room_batch.py
+++ b/synapse/rest/client/room_batch.py
@@ -15,13 +15,12 @@
 import logging
 import re
 from http import HTTPStatus
-from typing import TYPE_CHECKING, Awaitable, List, Tuple
+from typing import TYPE_CHECKING, Awaitable, Tuple
 
 from twisted.web.server import Request
 
-from synapse.api.constants import EventContentFields, EventTypes
+from synapse.api.constants import EventContentFields
 from synapse.api.errors import AuthError, Codes, SynapseError
-from synapse.appservice import ApplicationService
 from synapse.http.server import HttpServer
 from synapse.http.servlet import (
     RestServlet,
@@ -32,7 +31,7 @@
 )
 from synapse.http.site import SynapseRequest
 from synapse.rest.client.transactions import HttpTransactionCache
-from synapse.types import JsonDict, Requester, UserID, create_requester
+from synapse.types import JsonDict
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:
@@ -77,102 +76,12 @@ class RoomBatchSendEventRestServlet(RestServlet):
 
     def __init__(self, hs: "HomeServer"):
         super().__init__()
-        self.hs = hs
         self.store = hs.get_datastore()
-        self.state_store = hs.get_storage().state
         self.event_creation_handler = hs.get_event_creation_handler()
-        self.room_member_handler = hs.get_room_member_handler()
         self.auth = hs.get_auth()
+        self.room_batch_handler = hs.get_room_batch_handler()
         self.txns = HttpTransactionCache(hs)
 
-    async def _inherit_depth_from_prev_ids(self, prev_event_ids: List[str]) -> int:
-        (
-            most_recent_prev_event_id,
-            most_recent_prev_event_depth,
-        ) = await self.store.get_max_depth_of(prev_event_ids)
-
-        # We want to insert the historical event after the `prev_event` but before the successor event
-        #
-        # We inherit depth from the successor event instead of the `prev_event`
-        # because events returned from `/messages` are first sorted by `topological_ordering`
-        # which is just the `depth` and then tie-break with `stream_ordering`.
-        #
-        # We mark these inserted historical events as "backfilled" which gives them a
-        # negative `stream_ordering`. If we use the same depth as the `prev_event`,
-        # then our historical event will tie-break and be sorted before the `prev_event`
-        # when it should come after.
-        #
-        # We want to use the successor event depth so they appear after `prev_event` because
-        # it has a larger `depth` but before the successor event because the `stream_ordering`
-        # is negative before the successor event.
-        successor_event_ids = await self.store.get_successor_events(
-            [most_recent_prev_event_id]
-        )
-
-        # If we can't find any successor events, then it's a forward extremity of
-        # historical messages and we can just inherit from the previous historical
-        # event which we can already assume has the correct depth where we want
-        # to insert into.
-        if not successor_event_ids:
-            depth = most_recent_prev_event_depth
-        else:
-            (
-                _,
-                oldest_successor_depth,
-            ) = await self.store.get_min_depth_of(successor_event_ids)
-
-            depth = oldest_successor_depth
-
-        return depth
-
-    def _create_insertion_event_dict(
-        self, sender: str, room_id: str, origin_server_ts: int
-    ) -> JsonDict:
-        """Creates an event dict for an "insertion" event with the proper fields
-        and a random batch ID.
-
-        Args:
-            sender: The event author MXID
-            room_id: The room ID that the event belongs to
-            origin_server_ts: Timestamp when the event was sent
-
-        Returns:
-            The new event dictionary to insert.
-        """
-
-        next_batch_id = random_string(8)
-        insertion_event = {
-            "type": EventTypes.MSC2716_INSERTION,
-            "sender": sender,
-            "room_id": room_id,
-            "content": {
-                EventContentFields.MSC2716_NEXT_BATCH_ID: next_batch_id,
-                EventContentFields.MSC2716_HISTORICAL: True,
-            },
-            "origin_server_ts": origin_server_ts,
-        }
-
-        return insertion_event
-
-    async def _create_requester_for_user_id_from_app_service(
-        self, user_id: str, app_service: ApplicationService
-    ) -> Requester:
-        """Creates a new requester for the given user_id
-        and validates that the app service is allowed to control
-        the given user.
-
-        Args:
-            user_id: The author MXID that the app service is controlling
-            app_service: The app service that controls the user
-
-        Returns:
-            Requester object
-        """
-
-        await self.auth.validate_appservice_can_control_user_id(app_service, user_id)
-
-        return create_requester(user_id, app_service=app_service)
-
     async def on_POST(
         self, request: SynapseRequest, room_id: str
     ) -> Tuple[int, JsonDict]:
@@ -200,121 +109,62 @@ async def on_POST(
                 errcode=Codes.MISSING_PARAM,
             )
 
+        # Verify the batch_id_from_query corresponds to an actual insertion event
+        # and have the batch connected.
+        if batch_id_from_query:
+            corresponding_insertion_event_id = (
+                await self.store.get_insertion_event_by_batch_id(
+                    room_id, batch_id_from_query
+                )
+            )
+            if corresponding_insertion_event_id is None:
+                raise SynapseError(
+                    HTTPStatus.BAD_REQUEST,
+                    "No insertion event corresponds to the given ?batch_id",
+                    errcode=Codes.INVALID_PARAM,
+                )
+
         # For the event we are inserting next to (`prev_event_ids_from_query`),
         # find the most recent auth events (derived from state events) that
         # allowed that message to be sent. We will use that as a base
         # to auth our historical messages against.
-        (
-            most_recent_prev_event_id,
-            _,
-        ) = await self.store.get_max_depth_of(prev_event_ids_from_query)
-        # mapping from (type, state_key) -> state_event_id
-        prev_state_map = await self.state_store.get_state_ids_for_event(
-            most_recent_prev_event_id
+        auth_event_ids = await self.room_batch_handler.get_most_recent_auth_event_ids_from_event_id_list(
+            prev_event_ids_from_query
         )
-        # List of state event ID's
-        prev_state_ids = list(prev_state_map.values())
-        auth_event_ids = prev_state_ids
-
-        state_event_ids_at_start = []
-        for state_event in body["state_events_at_start"]:
-            assert_params_in_dict(
-                state_event, ["type", "origin_server_ts", "content", "sender"]
-            )
 
-            logger.debug(
-                "RoomBatchSendEventRestServlet inserting state_event=%s, auth_event_ids=%s",
-                state_event,
-                auth_event_ids,
+        # Create and persist all of the state events that float off on their own
+        # before the batch. These will most likely be all of the invite/member
+        # state events used to auth the upcoming historical messages.
+        state_event_ids_at_start = (
+            await self.room_batch_handler.persist_state_events_at_start(
+                state_events_at_start=body["state_events_at_start"],
+                room_id=room_id,
+                initial_auth_event_ids=auth_event_ids,
+                app_service_requester=requester,
             )
+        )
+        # Update our ongoing auth event ID list with all of the new state we
+        # just created
+        auth_event_ids.extend(state_event_ids_at_start)
 
-            event_dict = {
-                "type": state_event["type"],
-                "origin_server_ts": state_event["origin_server_ts"],
-                "content": state_event["content"],
-                "room_id": room_id,
-                "sender": state_event["sender"],
-                "state_key": state_event["state_key"],
-            }
-
-            # Mark all events as historical
-            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
-
-            # Make the state events float off on their own
-            fake_prev_event_id = "$" + random_string(43)
-
-            # TODO: This is pretty much the same as some other code to handle inserting state in this file
-            if event_dict["type"] == EventTypes.Member:
-                membership = event_dict["content"].get("membership", None)
-                event_id, _ = await self.room_member_handler.update_membership(
-                    await self._create_requester_for_user_id_from_app_service(
-                        state_event["sender"], requester.app_service
-                    ),
-                    target=UserID.from_string(event_dict["state_key"]),
-                    room_id=room_id,
-                    action=membership,
-                    content=event_dict["content"],
-                    outlier=True,
-                    prev_event_ids=[fake_prev_event_id],
-                    # Make sure to use a copy of this list because we modify it
-                    # later in the loop here. Otherwise it will be the same
-                    # reference and also update in the event when we append later.
-                    auth_event_ids=auth_event_ids.copy(),
-                )
-            else:
-                # TODO: Add some complement tests that adds state that is not member joins
-                # and will use this code path. Maybe we only want to support join state events
-                # and can get rid of this `else`?
-                (
-                    event,
-                    _,
-                ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                    await self._create_requester_for_user_id_from_app_service(
-                        state_event["sender"], requester.app_service
-                    ),
-                    event_dict,
-                    outlier=True,
-                    prev_event_ids=[fake_prev_event_id],
-                    # Make sure to use a copy of this list because we modify it
-                    # later in the loop here. Otherwise it will be the same
-                    # reference and also update in the event when we append later.
-                    auth_event_ids=auth_event_ids.copy(),
-                )
-                event_id = event.event_id
-
-            state_event_ids_at_start.append(event_id)
-            auth_event_ids.append(event_id)
-
-        events_to_create = body["events"]
-
-        inherited_depth = await self._inherit_depth_from_prev_ids(
+        inherited_depth = await self.room_batch_handler.inherit_depth_from_prev_ids(
             prev_event_ids_from_query
         )
 
+        events_to_create = body["events"]
+
         # Figure out which batch to connect to. If they passed in
         # batch_id_from_query let's use it. The batch ID passed in comes
         # from the batch_id in the "insertion" event from the previous batch.
         last_event_in_batch = events_to_create[-1]
-        batch_id_to_connect_to = batch_id_from_query
         base_insertion_event = None
         if batch_id_from_query:
+            batch_id_to_connect_to = batch_id_from_query
             #  All but the first base insertion event should point at a fake
             #  event, which causes the HS to ask for the state at the start of
             #  the batch later.
+            fake_prev_event_id = "$" + random_string(43)
             prev_event_ids = [fake_prev_event_id]
-
-            # Verify the batch_id_from_query corresponds to an actual insertion event
-            # and have the batch connected.
-            corresponding_insertion_event_id = (
-                await self.store.get_insertion_event_by_batch_id(batch_id_from_query)
-            )
-            if corresponding_insertion_event_id is None:
-                raise SynapseError(
-                    400,
-                    "No insertion event corresponds to the given ?batch_id",
-                    errcode=Codes.INVALID_PARAM,
-                )
-            pass
         # Otherwise, create an insertion event to act as a starting point.
         #
         # We don't always have an insertion event to start hanging more history
@@ -325,10 +175,12 @@ async def on_POST(
         else:
             prev_event_ids = prev_event_ids_from_query
 
-            base_insertion_event_dict = self._create_insertion_event_dict(
-                sender=requester.user.to_string(),
-                room_id=room_id,
-                origin_server_ts=last_event_in_batch["origin_server_ts"],
+            base_insertion_event_dict = (
+                self.room_batch_handler.create_insertion_event_dict(
+                    sender=requester.user.to_string(),
+                    room_id=room_id,
+                    origin_server_ts=last_event_in_batch["origin_server_ts"],
+                )
             )
             base_insertion_event_dict["prev_events"] = prev_event_ids.copy()
 
@@ -336,7 +188,7 @@ async def on_POST(
                 base_insertion_event,
                 _,
             ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                await self._create_requester_for_user_id_from_app_service(
+                await self.room_batch_handler.create_requester_for_user_id_from_app_service(
                     base_insertion_event_dict["sender"],
                     requester.app_service,
                 ),
@@ -351,92 +203,17 @@ async def on_POST(
                 EventContentFields.MSC2716_NEXT_BATCH_ID
             ]
 
-        # Connect this current batch to the insertion event from the previous batch
-        batch_event = {
-            "type": EventTypes.MSC2716_BATCH,
-            "sender": requester.user.to_string(),
-            "room_id": room_id,
-            "content": {
-                EventContentFields.MSC2716_BATCH_ID: batch_id_to_connect_to,
-                EventContentFields.MSC2716_HISTORICAL: True,
-            },
-            # Since the batch event is put at the end of the batch,
-            # where the newest-in-time event is, copy the origin_server_ts from
-            # the last event we're inserting
-            "origin_server_ts": last_event_in_batch["origin_server_ts"],
-        }
-        # Add the batch event to the end of the batch (newest-in-time)
-        events_to_create.append(batch_event)
-
-        # Add an "insertion" event to the start of each batch (next to the oldest-in-time
-        # event in the batch) so the next batch can be connected to this one.
-        insertion_event = self._create_insertion_event_dict(
-            sender=requester.user.to_string(),
+        # Create and persist all of the historical events as well as insertion
+        # and batch meta events to make the batch navigable in the DAG.
+        event_ids, next_batch_id = await self.room_batch_handler.handle_batch_of_events(
+            events_to_create=events_to_create,
             room_id=room_id,
-            # Since the insertion event is put at the start of the batch,
-            # where the oldest-in-time event is, copy the origin_server_ts from
-            # the first event we're inserting
-            origin_server_ts=events_to_create[0]["origin_server_ts"],
+            batch_id_to_connect_to=batch_id_to_connect_to,
+            initial_prev_event_ids=prev_event_ids,
+            inherited_depth=inherited_depth,
+            auth_event_ids=auth_event_ids,
+            app_service_requester=requester,
         )
-        # Prepend the insertion event to the start of the batch (oldest-in-time)
-        events_to_create = [insertion_event] + events_to_create
-
-        event_ids = []
-        events_to_persist = []
-        for ev in events_to_create:
-            assert_params_in_dict(ev, ["type", "origin_server_ts", "content", "sender"])
-
-            event_dict = {
-                "type": ev["type"],
-                "origin_server_ts": ev["origin_server_ts"],
-                "content": ev["content"],
-                "room_id": room_id,
-                "sender": ev["sender"],  # requester.user.to_string(),
-                "prev_events": prev_event_ids.copy(),
-            }
-
-            # Mark all events as historical
-            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
-
-            event, context = await self.event_creation_handler.create_event(
-                await self._create_requester_for_user_id_from_app_service(
-                    ev["sender"], requester.app_service
-                ),
-                event_dict,
-                prev_event_ids=event_dict.get("prev_events"),
-                auth_event_ids=auth_event_ids,
-                historical=True,
-                depth=inherited_depth,
-            )
-            logger.debug(
-                "RoomBatchSendEventRestServlet inserting event=%s, prev_event_ids=%s, auth_event_ids=%s",
-                event,
-                prev_event_ids,
-                auth_event_ids,
-            )
-
-            assert self.hs.is_mine_id(event.sender), "User must be our own: %s" % (
-                event.sender,
-            )
-
-            events_to_persist.append((event, context))
-            event_id = event.event_id
-
-            event_ids.append(event_id)
-            prev_event_ids = [event_id]
-
-        # Persist events in reverse-chronological order so they have the
-        # correct stream_ordering as they are backfilled (which decrements).
-        # Events are sorted by (topological_ordering, stream_ordering)
-        # where topological_ordering is just depth.
-        for (event, context) in reversed(events_to_persist):
-            ev = await self.event_creation_handler.handle_new_client_event(
-                await self._create_requester_for_user_id_from_app_service(
-                    event["sender"], requester.app_service
-                ),
-                event=event,
-                context=context,
-            )
 
         insertion_event_id = event_ids[0]
         batch_event_id = event_ids[-1]
@@ -445,9 +222,7 @@ async def on_POST(
         response_dict = {
             "state_event_ids": state_event_ids_at_start,
             "event_ids": historical_event_ids,
-            "next_batch_id": insertion_event["content"][
-                EventContentFields.MSC2716_NEXT_BATCH_ID
-            ],
+            "next_batch_id": next_batch_id,
             "insertion_event_id": insertion_event_id,
             "batch_event_id": batch_event_id,
         }
diff --git a/synapse/rest/client/shared_rooms.py b/synapse/rest/client/shared_rooms.py
index 1d90493eb..09a46737d 100644
--- a/synapse/rest/client/shared_rooms.py
+++ b/synapse/rest/client/shared_rooms.py
@@ -42,7 +42,7 @@ def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
-        self.user_directory_active = hs.config.update_user_directory
+        self.user_directory_active = hs.config.server.update_user_directory
 
     async def on_GET(
         self, request: SynapseRequest, user_id: str
diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py
index 1259058b9..913216a7c 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -155,7 +155,7 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             try:
                 filter_object = json_decoder.decode(filter_id)
                 set_timeline_upper_limit(
-                    filter_object, self.hs.config.filter_timeline_limit
+                    filter_object, self.hs.config.server.filter_timeline_limit
                 )
             except Exception:
                 raise SynapseError(400, "Invalid filter JSON")
diff --git a/synapse/rest/client/user_directory.py b/synapse/rest/client/user_directory.py
index 756805b9f..d612432d9 100644
--- a/synapse/rest/client/user_directory.py
+++ b/synapse/rest/client/user_directory.py
@@ -70,12 +70,12 @@ async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
 
         body = parse_json_object_from_request(request)
 
-        if self.hs.config.user_directory_defer_to_id_server:
+        if self.hs.config.userdirectory.user_directory_defer_to_id_server:
             signed_body = sign_json(
                 body, self.hs.hostname, self.hs.config.signing_key[0]
             )
             url = "%s/_matrix/identity/api/v1/user_directory/search" % (
-                self.hs.config.user_directory_defer_to_id_server,
+                self.hs.config.userdirectory.user_directory_defer_to_id_server,
             )
             resp = await self.http_client.post_json_get_json(url, signed_body)
             return 200, resp
diff --git a/synapse/rest/client/voip.py b/synapse/rest/client/voip.py
index ea2b8aa45..ea7e02515 100644
--- a/synapse/rest/client/voip.py
+++ b/synapse/rest/client/voip.py
@@ -70,7 +70,7 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
             {
                 "username": username,
                 "password": password,
-                "ttl": userLifetime / 1000,
+                "ttl": userLifetime // 1000,
                 "uris": turnUris,
             },
         )
diff --git a/synapse/rest/media/v1/__init__.py b/synapse/rest/media/v1/__init__.py
index 3dd16d4bb..d5b74cddf 100644
--- a/synapse/rest/media/v1/__init__.py
+++ b/synapse/rest/media/v1/__init__.py
@@ -12,33 +12,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import PIL.Image
+from PIL.features import check_codec
 
 # check for JPEG support.
-try:
-    PIL.Image._getdecoder("rgb", "jpeg", None)
-except OSError as e:
-    if str(e).startswith("decoder jpeg not available"):
-        raise Exception(
-            "FATAL: jpeg codec not supported. Install pillow correctly! "
-            " 'sudo apt-get install libjpeg-dev' then 'pip uninstall pillow &&"
-            " pip install pillow --user'"
-        )
-except Exception:
-    # any other exception is fine
-    pass
+if not check_codec("jpg"):
+    raise Exception(
+        "FATAL: jpeg codec not supported. Install pillow correctly! "
+        " 'sudo apt-get install libjpeg-dev' then 'pip uninstall pillow &&"
+        " pip install pillow --user'"
+    )
 
 
 # check for PNG support.
-try:
-    PIL.Image._getdecoder("rgb", "zip", None)
-except OSError as e:
-    if str(e).startswith("decoder zip not available"):
-        raise Exception(
-            "FATAL: zip codec not supported. Install pillow correctly! "
-            " 'sudo apt-get install libjpeg-dev' then 'pip uninstall pillow &&"
-            " pip install pillow --user'"
-        )
-except Exception:
-    # any other exception is fine
-    pass
+if not check_codec("zlib"):
+    raise Exception(
+        "FATAL: zip codec not supported. Install pillow correctly! "
+        " 'sudo apt-get install libjpeg-dev' then 'pip uninstall pillow &&"
+        " pip install pillow --user'"
+    )
diff --git a/synapse/rest/media/v1/oembed.py b/synapse/rest/media/v1/oembed.py
index e04671fb9..78b1603f1 100644
--- a/synapse/rest/media/v1/oembed.py
+++ b/synapse/rest/media/v1/oembed.py
@@ -96,6 +96,32 @@ def get_oembed_url(self, url: str) -> Optional[str]:
         # No match.
         return None
 
+    def autodiscover_from_html(self, tree: "etree.Element") -> Optional[str]:
+        """
+        Search an HTML document for oEmbed autodiscovery information.
+
+        Args:
+            tree: The parsed HTML body.
+
+        Returns:
+            The URL to use for oEmbed information, or None if no URL was found.
+        """
+        # Search for link elements with the proper rel and type attributes.
+        for tag in tree.xpath(
+            "//link[@rel='alternate'][@type='application/json+oembed']"
+        ):
+            if "href" in tag.attrib:
+                return tag.attrib["href"]
+
+        # Some providers (e.g. Flickr) use alternative instead of alternate.
+        for tag in tree.xpath(
+            "//link[@rel='alternative'][@type='application/json+oembed']"
+        ):
+            if "href" in tag.attrib:
+                return tag.attrib["href"]
+
+        return None
+
     def parse_oembed_response(self, url: str, raw_body: bytes) -> OEmbedResult:
         """
         Parse the oEmbed response into an Open Graph response.
@@ -165,7 +191,7 @@ def parse_oembed_response(self, url: str, raw_body: bytes) -> OEmbedResult:
 
         except Exception as e:
             # Trap any exception and let the code follow as usual.
-            logger.warning(f"Error parsing oEmbed metadata from {url}: {e:r}")
+            logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
             open_graph_response = {}
             cache_age = None
 
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 79a42b245..1fe0fc8aa 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -22,7 +22,7 @@
 import shutil
 import sys
 import traceback
-from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Union
+from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Tuple, Union
 from urllib import parse as urlparse
 
 import attr
@@ -73,6 +73,7 @@
 
 ONE_HOUR = 60 * 60 * 1000
 ONE_DAY = 24 * ONE_HOUR
+IMAGE_CACHE_EXPIRY_MS = 2 * ONE_DAY
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
@@ -295,22 +296,32 @@ async def _do_preview(self, url: str, user: str, ts: int) -> bytes:
                 body = file.read()
 
             encoding = get_html_media_encoding(body, media_info.media_type)
-            og = decode_and_calc_og(body, media_info.uri, encoding)
-
-            await self._precache_image_url(user, media_info, og)
-
-        elif oembed_url and _is_json(media_info.media_type):
-            # Handle an oEmbed response.
-            with open(media_info.filename, "rb") as file:
-                body = file.read()
-
-            oembed_response = self._oembed.parse_oembed_response(url, body)
-            og = oembed_response.open_graph_result
-
-            # Use the cache age from the oEmbed result, instead of the HTTP response.
-            if oembed_response.cache_age is not None:
-                expiration_ms = oembed_response.cache_age
+            tree = decode_body(body, encoding)
+            if tree is not None:
+                # Check if this HTML document points to oEmbed information and
+                # defer to that.
+                oembed_url = self._oembed.autodiscover_from_html(tree)
+                og = {}
+                if oembed_url:
+                    oembed_info = await self._download_url(oembed_url, user)
+                    og, expiration_ms = await self._handle_oembed_response(
+                        url, oembed_info, expiration_ms
+                    )
+
+                # If there was no oEmbed URL (or oEmbed parsing failed), attempt
+                # to generate the Open Graph information from the HTML.
+                if not oembed_url or not og:
+                    og = _calc_og(tree, media_info.uri)
+
+                await self._precache_image_url(user, media_info, og)
+            else:
+                og = {}
 
+        elif oembed_url:
+            # Handle the oEmbed information.
+            og, expiration_ms = await self._handle_oembed_response(
+                url, media_info, expiration_ms
+            )
             await self._precache_image_url(user, media_info, og)
 
         else:
@@ -478,6 +489,39 @@ async def _precache_image_url(
         else:
             del og["og:image"]
 
+    async def _handle_oembed_response(
+        self, url: str, media_info: MediaInfo, expiration_ms: int
+    ) -> Tuple[JsonDict, int]:
+        """
+        Parse the downloaded oEmbed info.
+
+        Args:
+            url: The URL which is being previewed (not the one which was
+                requested).
+            media_info: The media being previewed.
+            expiration_ms: The length of time, in milliseconds, the media is valid for.
+
+        Returns:
+            A tuple of:
+                The Open Graph dictionary, if the oEmbed info can be parsed.
+                The (possibly updated) length of time, in milliseconds, the media is valid for.
+        """
+        # If JSON was not returned, there's nothing to do.
+        if not _is_json(media_info.media_type):
+            return {}, expiration_ms
+
+        with open(media_info.filename, "rb") as file:
+            body = file.read()
+
+        oembed_response = self._oembed.parse_oembed_response(url, body)
+        open_graph_result = oembed_response.open_graph_result
+
+        # Use the cache age from the oEmbed result, if one was given.
+        if open_graph_result and oembed_response.cache_age is not None:
+            expiration_ms = oembed_response.cache_age
+
+        return open_graph_result, expiration_ms
+
     def _start_expire_url_cache_data(self) -> Deferred:
         return run_as_background_process(
             "expire_url_cache_data", self._expire_url_cache_data
@@ -496,6 +540,27 @@ async def _expire_url_cache_data(self) -> None:
             logger.info("Still running DB updates; skipping expiry")
             return
 
+        def try_remove_parent_dirs(dirs: Iterable[str]) -> None:
+            """Attempt to remove the given chain of parent directories
+
+            Args:
+                dirs: The list of directory paths to delete, with children appearing
+                    before their parents.
+            """
+            for dir in dirs:
+                try:
+                    os.rmdir(dir)
+                except FileNotFoundError:
+                    # Already deleted, continue with deleting the rest
+                    pass
+                except OSError as e:
+                    # Failed, skip deleting the rest of the parent dirs
+                    if e.errno != errno.ENOTEMPTY:
+                        logger.warning(
+                            "Failed to remove media directory: %r: %s", dir, e
+                        )
+                    break
+
         # First we delete expired url cache entries
         media_ids = await self.store.get_expired_url_cache(now)
 
@@ -504,20 +569,16 @@ async def _expire_url_cache_data(self) -> None:
             fname = self.filepaths.url_cache_filepath(media_id)
             try:
                 os.remove(fname)
+            except FileNotFoundError:
+                pass  # If the path doesn't exist, meh
             except OSError as e:
-                # If the path doesn't exist, meh
-                if e.errno != errno.ENOENT:
-                    logger.warning("Failed to remove media: %r: %s", media_id, e)
-                    continue
+                logger.warning("Failed to remove media: %r: %s", media_id, e)
+                continue
 
             removed_media.append(media_id)
 
-            try:
-                dirs = self.filepaths.url_cache_filepath_dirs_to_delete(media_id)
-                for dir in dirs:
-                    os.rmdir(dir)
-            except Exception:
-                pass
+            dirs = self.filepaths.url_cache_filepath_dirs_to_delete(media_id)
+            try_remove_parent_dirs(dirs)
 
         await self.store.delete_url_cache(removed_media)
 
@@ -530,7 +591,7 @@ async def _expire_url_cache_data(self) -> None:
         # These may be cached for a bit on the client (i.e., they
         # may have a room open with a preview url thing open).
         # So we wait a couple of days before deleting, just in case.
-        expire_before = now - 2 * ONE_DAY
+        expire_before = now - IMAGE_CACHE_EXPIRY_MS
         media_ids = await self.store.get_url_cache_media_before(expire_before)
 
         removed_media = []
@@ -538,36 +599,30 @@ async def _expire_url_cache_data(self) -> None:
             fname = self.filepaths.url_cache_filepath(media_id)
             try:
                 os.remove(fname)
+            except FileNotFoundError:
+                pass  # If the path doesn't exist, meh
             except OSError as e:
-                # If the path doesn't exist, meh
-                if e.errno != errno.ENOENT:
-                    logger.warning("Failed to remove media: %r: %s", media_id, e)
-                    continue
+                logger.warning("Failed to remove media: %r: %s", media_id, e)
+                continue
 
-            try:
-                dirs = self.filepaths.url_cache_filepath_dirs_to_delete(media_id)
-                for dir in dirs:
-                    os.rmdir(dir)
-            except Exception:
-                pass
+            dirs = self.filepaths.url_cache_filepath_dirs_to_delete(media_id)
+            try_remove_parent_dirs(dirs)
 
             thumbnail_dir = self.filepaths.url_cache_thumbnail_directory(media_id)
             try:
                 shutil.rmtree(thumbnail_dir)
+            except FileNotFoundError:
+                pass  # If the path doesn't exist, meh
             except OSError as e:
-                # If the path doesn't exist, meh
-                if e.errno != errno.ENOENT:
-                    logger.warning("Failed to remove media: %r: %s", media_id, e)
-                    continue
+                logger.warning("Failed to remove media: %r: %s", media_id, e)
+                continue
 
             removed_media.append(media_id)
 
-            try:
-                dirs = self.filepaths.url_cache_thumbnail_dirs_to_delete(media_id)
-                for dir in dirs:
-                    os.rmdir(dir)
-            except Exception:
-                pass
+            dirs = self.filepaths.url_cache_thumbnail_dirs_to_delete(media_id)
+            # Note that one of the directories to be deleted has already been
+            # removed by the `rmtree` above.
+            try_remove_parent_dirs(dirs)
 
         await self.store.delete_url_cache_media(removed_media)
 
@@ -619,26 +674,22 @@ def get_html_media_encoding(body: bytes, content_type: str) -> str:
     return "utf-8"
 
 
-def decode_and_calc_og(
-    body: bytes, media_uri: str, request_encoding: Optional[str] = None
-) -> JsonDict:
+def decode_body(
+    body: bytes, request_encoding: Optional[str] = None
+) -> Optional["etree.Element"]:
     """
-    Calculate metadata for an HTML document.
-
-    This uses lxml to parse the HTML document into the OG response. If errors
-    occur during processing of the document, an empty response is returned.
+    This uses lxml to parse the HTML document.
 
     Args:
         body: The HTML document, as bytes.
-        media_url: The URI used to download the body.
         request_encoding: The character encoding of the body, as a string.
 
     Returns:
-        The OG response as a dictionary.
+        The parsed HTML body, or None if an error occurred during processed.
     """
     # If there's no body, nothing useful is going to be found.
     if not body:
-        return {}
+        return None
 
     from lxml import etree
 
@@ -650,25 +701,22 @@ def decode_and_calc_og(
         parser = etree.HTMLParser(recover=True, encoding="utf-8")
     except Exception as e:
         logger.warning("Unable to create HTML parser: %s" % (e,))
-        return {}
-
-    def _attempt_calc_og(body_attempt: Union[bytes, str]) -> Dict[str, Optional[str]]:
-        # Attempt to parse the body. If this fails, log and return no metadata.
-        tree = etree.fromstring(body_attempt, parser)
-
-        # The data was successfully parsed, but no tree was found.
-        if tree is None:
-            return {}
+        return None
 
-        return _calc_og(tree, media_uri)
+    def _attempt_decode_body(
+        body_attempt: Union[bytes, str]
+    ) -> Optional["etree.Element"]:
+        # Attempt to parse the body. Returns None if the body was successfully
+        # parsed, but no tree was found.
+        return etree.fromstring(body_attempt, parser)
 
     # Attempt to parse the body. If this fails, log and return no metadata.
     try:
-        return _attempt_calc_og(body)
+        return _attempt_decode_body(body)
     except UnicodeDecodeError:
         # blindly try decoding the body as utf-8, which seems to fix
         # the charset mismatches on https://google.com
-        return _attempt_calc_og(body.decode("utf-8", "ignore"))
+        return _attempt_decode_body(body.decode("utf-8", "ignore"))
 
 
 def _calc_og(tree: "etree.Element", media_uri: str) -> Dict[str, Optional[str]]:
diff --git a/synapse/rest/media/v1/thumbnailer.py b/synapse/rest/media/v1/thumbnailer.py
index df54a4064..46701a8b8 100644
--- a/synapse/rest/media/v1/thumbnailer.py
+++ b/synapse/rest/media/v1/thumbnailer.py
@@ -61,9 +61,19 @@ def __init__(self, input_path: str):
         self.transpose_method = None
         try:
             # We don't use ImageOps.exif_transpose since it crashes with big EXIF
-            image_exif = self.image._getexif()
+            #
+            # Ignore safety: Pillow seems to acknowledge that this method is
+            # "private, experimental, but generally widely used". Pillow 6
+            # includes a public getexif() method (no underscore) that we might
+            # consider using instead when we can bump that dependency.
+            #
+            # At the time of writing, Debian buster (currently oldstable)
+            # provides version 5.4.1. It's expected to EOL in mid-2022, see
+            # https://wiki.debian.org/DebianReleases#Production_Releases
+            image_exif = self.image._getexif()  # type: ignore
             if image_exif is not None:
                 image_orientation = image_exif.get(EXIF_ORIENTATION_TAG)
+                assert isinstance(image_orientation, int)
                 self.transpose_method = EXIF_TRANSPOSE_MAPPINGS.get(image_orientation)
         except Exception as e:
             # A lot of parsing errors can happen when parsing EXIF
@@ -76,7 +86,10 @@ def transpose(self) -> Tuple[int, int]:
             A tuple containing the new image size in pixels as (width, height).
         """
         if self.transpose_method is not None:
-            self.image = self.image.transpose(self.transpose_method)
+            # Safety: `transpose` takes an int rather than e.g. an IntEnum.
+            # self.transpose_method is set above to be a value in
+            # EXIF_TRANSPOSE_MAPPINGS, and that only contains correct values.
+            self.image = self.image.transpose(self.transpose_method)  # type: ignore[arg-type]
             self.width, self.height = self.image.size
             self.transpose_method = None
             # We don't need EXIF any more
@@ -101,7 +114,7 @@ def aspect(self, max_width: int, max_height: int) -> Tuple[int, int]:
         else:
             return (max_height * self.width) // self.height, max_height
 
-    def _resize(self, width: int, height: int) -> Image:
+    def _resize(self, width: int, height: int) -> Image.Image:
         # 1-bit or 8-bit color palette images need converting to RGB
         # otherwise they will be scaled using nearest neighbour which
         # looks awful.
@@ -151,7 +164,7 @@ def crop(self, width: int, height: int, output_type: str) -> BytesIO:
             cropped = scaled_image.crop((crop_left, 0, crop_right, height))
         return self._encode_image(cropped, output_type)
 
-    def _encode_image(self, output_image: Image, output_type: str) -> BytesIO:
+    def _encode_image(self, output_image: Image.Image, output_type: str) -> BytesIO:
         output_bytes_io = BytesIO()
         fmt = self.FORMATS[output_type]
         if fmt == "JPEG":
diff --git a/synapse/rest/well_known.py b/synapse/rest/well_known.py
index c80a3a99a..7ac01faab 100644
--- a/synapse/rest/well_known.py
+++ b/synapse/rest/well_known.py
@@ -39,9 +39,9 @@ def get_well_known(self) -> Optional[JsonDict]:
 
         result = {"m.homeserver": {"base_url": self._config.server.public_baseurl}}
 
-        if self._config.default_identity_server:
+        if self._config.registration.default_identity_server:
             result["m.identity_server"] = {
-                "base_url": self._config.default_identity_server
+                "base_url": self._config.registration.default_identity_server
             }
 
         return result
diff --git a/synapse/server.py b/synapse/server.py
index 637eb15b7..5bc045d61 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -39,7 +39,7 @@
 
 from synapse.api.auth import Auth
 from synapse.api.filtering import Filtering
-from synapse.api.ratelimiting import Ratelimiter
+from synapse.api.ratelimiting import Ratelimiter, RequestRatelimiter
 from synapse.appservice.api import ApplicationServiceApi
 from synapse.appservice.scheduler import ApplicationServiceScheduler
 from synapse.config.homeserver import HomeServerConfig
@@ -97,6 +97,7 @@
     RoomCreationHandler,
     RoomShutdownHandler,
 )
+from synapse.handlers.room_batch import RoomBatchHandler
 from synapse.handlers.room_list import RoomListHandler
 from synapse.handlers.room_member import RoomMemberHandler, RoomMemberMasterHandler
 from synapse.handlers.room_member_worker import RoomMemberWorkerHandler
@@ -437,6 +438,10 @@ def get_federation_http_client(self) -> MatrixFederationHttpClient:
     def get_room_creation_handler(self) -> RoomCreationHandler:
         return RoomCreationHandler(self)
 
+    @cache_in_self
+    def get_room_batch_handler(self) -> RoomBatchHandler:
+        return RoomBatchHandler(self)
+
     @cache_in_self
     def get_room_shutdown_handler(self) -> RoomShutdownHandler:
         return RoomShutdownHandler(self)
@@ -816,3 +821,12 @@ def get_outbound_redis_connection(self) -> Optional["RedisProtocol"]:
     def should_send_federation(self) -> bool:
         "Should this server be sending federation traffic directly?"
         return self.config.worker.send_federation
+
+    @cache_in_self
+    def get_request_ratelimiter(self) -> RequestRatelimiter:
+        return RequestRatelimiter(
+            self.get_datastore(),
+            self.get_clock(),
+            self.config.ratelimiting.rc_message,
+            self.config.ratelimiting.rc_admin_redaction,
+        )
diff --git a/synapse/server_notices/resource_limits_server_notices.py b/synapse/server_notices/resource_limits_server_notices.py
index 073b0d754..8522930b5 100644
--- a/synapse/server_notices/resource_limits_server_notices.py
+++ b/synapse/server_notices/resource_limits_server_notices.py
@@ -47,9 +47,9 @@ def __init__(self, hs: "HomeServer"):
         self._notifier = hs.get_notifier()
 
         self._enabled = (
-            hs.config.limit_usage_by_mau
+            hs.config.server.limit_usage_by_mau
             and self._server_notices_manager.is_enabled()
-            and not hs.config.hs_disabled
+            and not hs.config.server.hs_disabled
         )
 
     async def maybe_send_server_notice_to_user(self, user_id: str) -> None:
@@ -98,7 +98,7 @@ async def maybe_send_server_notice_to_user(self, user_id: str) -> None:
         try:
             if (
                 limit_type == LimitBlockingTypes.MONTHLY_ACTIVE_USER
-                and not self._config.mau_limit_alerting
+                and not self._config.server.mau_limit_alerting
             ):
                 # We have hit the MAU limit, but MAU alerting is disabled:
                 # reset room if necessary and return
@@ -149,7 +149,7 @@ async def _apply_limit_block_notification(
             "body": event_body,
             "msgtype": ServerNoticeMsgType,
             "server_notice_type": ServerNoticeLimitReached,
-            "admin_contact": self._config.admin_contact,
+            "admin_contact": self._config.server.admin_contact,
             "limit_type": event_limit_type,
         }
         event = await self._server_notices_manager.send_notice(
diff --git a/synapse/server_notices/server_notices_manager.py b/synapse/server_notices/server_notices_manager.py
index cd1c5ff6f..0cf60236f 100644
--- a/synapse/server_notices/server_notices_manager.py
+++ b/synapse/server_notices/server_notices_manager.py
@@ -41,12 +41,8 @@ def __init__(self, hs: "HomeServer"):
         self._notifier = hs.get_notifier()
         self.server_notices_mxid = self._config.servernotices.server_notices_mxid
 
-    def is_enabled(self):
-        """Checks if server notices are enabled on this server.
-
-        Returns:
-            bool
-        """
+    def is_enabled(self) -> bool:
+        """Checks if server notices are enabled on this server."""
         return self.server_notices_mxid is not None
 
     async def send_notice(
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index c981df3f1..5cf2e1257 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -118,7 +118,7 @@ def __init__(
         else:
             self.state_id = _gen_state_id()
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self.state)
 
 
diff --git a/synapse/state/v1.py b/synapse/state/v1.py
index 92336d7cc..ffe6207a3 100644
--- a/synapse/state/v1.py
+++ b/synapse/state/v1.py
@@ -225,7 +225,7 @@ def _resolve_with_state(
     conflicted_state_ids: StateMap[Set[str]],
     auth_event_ids: StateMap[str],
     state_map: Dict[str, EventBase],
-):
+) -> MutableStateMap[str]:
     conflicted_state = {}
     for key, event_ids in conflicted_state_ids.items():
         events = [state_map[ev_id] for ev_id in event_ids if ev_id in state_map]
@@ -329,12 +329,10 @@ def _resolve_auth_events(
         auth_events[(prev_event.type, prev_event.state_key)] = prev_event
         try:
             # The signatures have already been checked at this point
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V1,
                 event,
                 auth_events,
-                do_sig_check=False,
-                do_size_check=False,
             )
             prev_event = event
         except AuthError:
@@ -349,12 +347,10 @@ def _resolve_normal_events(
     for event in _ordered_events(events):
         try:
             # The signatures have already been checked at this point
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V1,
                 event,
                 auth_events,
-                do_sig_check=False,
-                do_size_check=False,
             )
             return event
         except AuthError:
@@ -366,7 +362,7 @@ def _resolve_normal_events(
 
 
 def _ordered_events(events: Iterable[EventBase]) -> List[EventBase]:
-    def key_func(e):
+    def key_func(e: EventBase) -> Tuple[int, str]:
         # we have to use utf-8 rather than ascii here because it turns out we allow
         # people to send us events with non-ascii event IDs :/
         return -int(e.depth), hashlib.sha1(e.event_id.encode("utf-8")).hexdigest()
diff --git a/synapse/state/v2.py b/synapse/state/v2.py
index 7b1e8361d..bd18eefd5 100644
--- a/synapse/state/v2.py
+++ b/synapse/state/v2.py
@@ -481,7 +481,7 @@ async def _reverse_topological_power_sort(
         if idx % _AWAIT_AFTER_ITERATIONS == 0:
             await clock.sleep(0)
 
-    def _get_power_order(event_id):
+    def _get_power_order(event_id: str) -> Tuple[int, int, str]:
         ev = event_map[event_id]
         pl = event_to_pl[event_id]
 
@@ -546,12 +546,10 @@ async def _iterative_auth_checks(
                     auth_events[key] = event_map[ev_id]
 
         try:
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 room_version,
                 event,
                 auth_events,
-                do_sig_check=False,
-                do_size_check=False,
             )
 
             resolved_state[(event.type, event.state_key)] = event_id
diff --git a/synapse/storage/databases/main/censor_events.py b/synapse/storage/databases/main/censor_events.py
index 6305414e3..eee07227e 100644
--- a/synapse/storage/databases/main/censor_events.py
+++ b/synapse/storage/databases/main/censor_events.py
@@ -36,7 +36,7 @@ def __init__(self, database: DatabasePool, db_conn, hs: "HomeServer"):
 
         if (
             hs.config.worker.run_background_tasks
-            and self.hs.config.redaction_retention_period is not None
+            and self.hs.config.server.redaction_retention_period is not None
         ):
             hs.get_clock().looping_call(self._censor_redactions, 5 * 60 * 1000)
 
@@ -48,7 +48,7 @@ async def _censor_redactions(self):
         By censor we mean update the event_json table with the redacted event.
         """
 
-        if self.hs.config.redaction_retention_period is None:
+        if self.hs.config.server.redaction_retention_period is None:
             return
 
         if not (
@@ -60,7 +60,9 @@ async def _censor_redactions(self):
             # created.
             return
 
-        before_ts = self._clock.time_msec() - self.hs.config.redaction_retention_period
+        before_ts = (
+            self._clock.time_msec() - self.hs.config.server.redaction_retention_period
+        )
 
         # We fetch all redactions that:
         #   1. point to an event we have,
diff --git a/synapse/storage/databases/main/client_ips.py b/synapse/storage/databases/main/client_ips.py
index cc192f5c8..6c1ef0904 100644
--- a/synapse/storage/databases/main/client_ips.py
+++ b/synapse/storage/databases/main/client_ips.py
@@ -353,7 +353,7 @@ class ClientIpWorkerStore(ClientIpBackgroundUpdateStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
-        self.user_ips_max_age = hs.config.user_ips_max_age
+        self.user_ips_max_age = hs.config.server.user_ips_max_age
 
         if hs.config.worker.run_background_tasks and self.user_ips_max_age:
             self._clock.looping_call(self._prune_old_user_ips, 5 * 1000)
@@ -538,15 +538,20 @@ async def get_last_client_ip_by_device(
         """
         ret = await super().get_last_client_ip_by_device(user_id, device_id)
 
-        # Update what is retrieved from the database with data which is pending insertion.
+        # Update what is retrieved from the database with data which is pending
+        # insertion, as if it has already been stored in the database.
         for key in self._batch_row_update:
-            uid, access_token, ip = key
+            uid, _access_token, ip = key
             if uid == user_id:
                 user_agent, did, last_seen = self._batch_row_update[key]
+
+                if did is None:
+                    # These updates don't make it to the `devices` table
+                    continue
+
                 if not device_id or did == device_id:
-                    ret[(user_id, device_id)] = {
+                    ret[(user_id, did)] = {
                         "user_id": user_id,
-                        "access_token": access_token,
                         "ip": ip,
                         "user_agent": user_agent,
                         "device_id": did,
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 584f818ff..19f55c19c 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -104,7 +104,7 @@ def __init__(
         self._clock = hs.get_clock()
         self._instance_name = hs.get_instance_name()
 
-        self._ephemeral_messages_enabled = hs.config.enable_ephemeral_messages
+        self._ephemeral_messages_enabled = hs.config.server.enable_ephemeral_messages
         self.is_mine_id = hs.is_mine_id
 
         # Ideally we'd move these ID gens here, unfortunately some other ID
@@ -1276,13 +1276,6 @@ def _update_outliers_txn(self, txn, events_and_contexts):
                     logger.exception("")
                     raise
 
-                # update the stored internal_metadata to update the "outlier" flag.
-                # TODO: This is unused as of Synapse 1.31. Remove it once we are happy
-                #  to drop backwards-compatibility with 1.30.
-                metadata_json = json_encoder.encode(event.internal_metadata.get_dict())
-                sql = "UPDATE event_json SET internal_metadata = ? WHERE event_id = ?"
-                txn.execute(sql, (metadata_json, event.event_id))
-
                 # Add an entry to the ex_outlier_stream table to replicate the
                 # change in outlier status to our workers.
                 stream_order = event.internal_metadata.stream_ordering
@@ -1327,19 +1320,6 @@ def event_dict(event):
             d.pop("redacted_because", None)
             return d
 
-        def get_internal_metadata(event):
-            im = event.internal_metadata.get_dict()
-
-            # temporary hack for database compatibility with Synapse 1.30 and earlier:
-            # store the `outlier` flag inside the internal_metadata json as well as in
-            # the `events` table, so that if anyone rolls back to an older Synapse,
-            # things keep working. This can be removed once we are happy to drop support
-            # for that
-            if event.internal_metadata.is_outlier():
-                im["outlier"] = True
-
-            return im
-
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_json",
@@ -1348,7 +1328,7 @@ def get_internal_metadata(event):
                     "event_id": event.event_id,
                     "room_id": event.room_id,
                     "internal_metadata": json_encoder.encode(
-                        get_internal_metadata(event)
+                        event.internal_metadata.get_dict()
                     ),
                     "json": json_encoder.encode(event_dict(event)),
                     "format_version": event.format_version,
@@ -1783,9 +1763,8 @@ def _handle_insertion_event(self, txn: LoggingTransaction, event: EventBase):
             retcol="creator",
             allow_none=True,
         )
-        if (
-            not room_version.msc2716_historical
-            or not self.hs.config.experimental.msc2716_enabled
+        if not room_version.msc2716_historical and (
+            not self.hs.config.experimental.msc2716_enabled
             or event.sender != room_creator
         ):
             return
@@ -1845,9 +1824,8 @@ def _handle_batch_event(self, txn: LoggingTransaction, event: EventBase):
             retcol="creator",
             allow_none=True,
         )
-        if (
-            not room_version.msc2716_historical
-            or not self.hs.config.experimental.msc2716_enabled
+        if not room_version.msc2716_historical and (
+            not self.hs.config.experimental.msc2716_enabled
             or event.sender != room_creator
         ):
             return
diff --git a/synapse/storage/databases/main/filtering.py b/synapse/storage/databases/main/filtering.py
index bb244a03c..434986fa6 100644
--- a/synapse/storage/databases/main/filtering.py
+++ b/synapse/storage/databases/main/filtering.py
@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from typing import Union
+
 from canonicaljson import encode_canonical_json
 
 from synapse.api.errors import Codes, SynapseError
@@ -22,7 +24,9 @@
 
 class FilteringStore(SQLBaseStore):
     @cached(num_args=2)
-    async def get_user_filter(self, user_localpart, filter_id):
+    async def get_user_filter(
+        self, user_localpart: str, filter_id: Union[int, str]
+    ) -> JsonDict:
         # filter_id is BIGINT UNSIGNED, so if it isn't a number, fail
         # with a coherent error message rather than 500 M_UNKNOWN.
         try:
@@ -40,7 +44,7 @@ async def get_user_filter(self, user_localpart, filter_id):
 
         return db_to_json(def_json)
 
-    async def add_user_filter(self, user_localpart: str, user_filter: JsonDict) -> str:
+    async def add_user_filter(self, user_localpart: str, user_filter: JsonDict) -> int:
         def_json = encode_canonical_json(user_filter)
 
         # Need an atomic transaction to SELECT the maximal ID so far then
diff --git a/synapse/storage/databases/main/monthly_active_users.py b/synapse/storage/databases/main/monthly_active_users.py
index b76ee51a9..ec4d47a56 100644
--- a/synapse/storage/databases/main/monthly_active_users.py
+++ b/synapse/storage/databases/main/monthly_active_users.py
@@ -32,8 +32,8 @@ def __init__(self, database: DatabasePool, db_conn, hs):
         self._clock = hs.get_clock()
         self.hs = hs
 
-        self._limit_usage_by_mau = hs.config.limit_usage_by_mau
-        self._max_mau_value = hs.config.max_mau_value
+        self._limit_usage_by_mau = hs.config.server.limit_usage_by_mau
+        self._max_mau_value = hs.config.server.max_mau_value
 
     @cached(num_args=0)
     async def get_monthly_active_count(self) -> int:
@@ -96,8 +96,8 @@ async def get_registered_reserved_users(self) -> List[str]:
         """
         users = []
 
-        for tp in self.hs.config.mau_limits_reserved_threepids[
-            : self.hs.config.max_mau_value
+        for tp in self.hs.config.server.mau_limits_reserved_threepids[
+            : self.hs.config.server.max_mau_value
         ]:
             user_id = await self.hs.get_datastore().get_user_id_by_threepid(
                 tp["medium"], tp["address"]
@@ -212,7 +212,7 @@ class MonthlyActiveUsersStore(MonthlyActiveUsersWorkerStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
-        self._mau_stats_only = hs.config.mau_stats_only
+        self._mau_stats_only = hs.config.server.mau_stats_only
 
         # Do not add more reserved users than the total allowable number
         self.db_pool.new_transaction(
@@ -221,7 +221,7 @@ def __init__(self, database: DatabasePool, db_conn, hs):
             [],
             [],
             self._initialise_reserved_users,
-            hs.config.mau_limits_reserved_threepids[: self._max_mau_value],
+            hs.config.server.mau_limits_reserved_threepids[: self._max_mau_value],
         )
 
     def _initialise_reserved_users(self, txn, threepids):
@@ -354,3 +354,27 @@ async def populate_monthly_active_users(self, user_id):
                         await self.upsert_monthly_active_user(user_id)
             elif now - last_seen_timestamp > LAST_SEEN_GRANULARITY:
                 await self.upsert_monthly_active_user(user_id)
+
+    async def remove_deactivated_user_from_mau_table(self, user_id: str) -> None:
+        """
+        Removes a deactivated user from the monthly active user
+        table and resets affected caches.
+
+        Args:
+            user_id(str): the user_id to remove
+        """
+
+        rows_deleted = await self.db_pool.simple_delete(
+            table="monthly_active_users",
+            keyvalues={"user_id": user_id},
+            desc="simple_delete",
+        )
+
+        if rows_deleted != 0:
+            await self.invalidate_cache_and_stream(
+                "user_last_seen_monthly_active", (user_id,)
+            )
+            await self.invalidate_cache_and_stream("get_monthly_active_count", ())
+            await self.invalidate_cache_and_stream(
+                "get_monthly_active_count_by_service", ()
+            )
diff --git a/synapse/storage/databases/main/push_rule.py b/synapse/storage/databases/main/push_rule.py
index a7fb8cd84..fc720f594 100644
--- a/synapse/storage/databases/main/push_rule.py
+++ b/synapse/storage/databases/main/push_rule.py
@@ -14,7 +14,7 @@
 # limitations under the License.
 import abc
 import logging
-from typing import List, Tuple, Union
+from typing import Dict, List, Tuple, Union
 
 from synapse.api.errors import NotFoundError, StoreError
 from synapse.push.baserules import list_with_base_rules
@@ -101,7 +101,9 @@ def __init__(self, database: DatabasePool, db_conn, hs):
             prefilled_cache=push_rules_prefill,
         )
 
-        self._users_new_default_push_rules = hs.config.users_new_default_push_rules
+        self._users_new_default_push_rules = (
+            hs.config.server.users_new_default_push_rules
+        )
 
     @abc.abstractmethod
     def get_max_push_rules_stream_id(self):
@@ -137,7 +139,7 @@ async def get_push_rules_for_user(self, user_id):
         return _load_rules(rows, enabled_map, use_new_defaults)
 
     @cached(max_entries=5000)
-    async def get_push_rules_enabled_for_user(self, user_id):
+    async def get_push_rules_enabled_for_user(self, user_id) -> Dict[str, bool]:
         results = await self.db_pool.simple_select_list(
             table="push_rules_enable",
             keyvalues={"user_name": user_id},
diff --git a/synapse/storage/databases/main/pusher.py b/synapse/storage/databases/main/pusher.py
index a93caae8d..b73ce53c9 100644
--- a/synapse/storage/databases/main/pusher.py
+++ b/synapse/storage/databases/main/pusher.py
@@ -18,8 +18,7 @@
 
 from synapse.push import PusherConfig, ThrottleParams
 from synapse.storage._base import SQLBaseStore, db_to_json
-from synapse.storage.database import DatabasePool
-from synapse.storage.types import Connection
+from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
 from synapse.storage.util.id_generators import StreamIdGenerator
 from synapse.types import JsonDict
 from synapse.util import json_encoder
@@ -32,7 +31,12 @@
 
 
 class PusherWorkerStore(SQLBaseStore):
-    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ):
         super().__init__(database, db_conn, hs)
         self._pushers_id_gen = StreamIdGenerator(
             db_conn, "pushers", "id", extra_tables=[("deleted_pushers", "stream_id")]
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 5ba4ca127..5e0df3865 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -26,7 +26,7 @@
 from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
 from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
 from synapse.storage.databases.main.stats import StatsStore
-from synapse.storage.types import Connection, Cursor
+from synapse.storage.types import Cursor
 from synapse.storage.util.id_generators import IdGenerator
 from synapse.storage.util.sequence import build_sequence_generator
 from synapse.types import UserID, UserInfo
@@ -207,7 +207,7 @@ async def is_trial_user(self, user_id: str) -> bool:
             return False
 
         now = self._clock.time_msec()
-        trial_duration_ms = self.config.mau_trial_days * 24 * 60 * 60 * 1000
+        trial_duration_ms = self.config.server.mau_trial_days * 24 * 60 * 60 * 1000
         is_trial = (now - info["creation_ts"] * 1000) < trial_duration_ms
         return is_trial
 
@@ -1790,7 +1790,7 @@ async def _bg_user_threepids_grandfather(self, progress, batch_size):
         We do this by grandfathering in existing user threepids assuming that
         they used one of the server configured trusted identity servers.
         """
-        id_servers = set(self.config.trusted_third_party_id_servers)
+        id_servers = set(self.config.registration.trusted_third_party_id_servers)
 
         def _bg_user_threepids_grandfather_txn(txn):
             sql = """
@@ -1855,10 +1855,17 @@ async def is_guest(self, user_id: str) -> bool:
 
 
 class RegistrationStore(StatsStore, RegistrationBackgroundUpdateStore):
-    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ):
         super().__init__(database, db_conn, hs)
 
-        self._ignore_unknown_session_error = hs.config.request_token_inhibit_3pid_errors
+        self._ignore_unknown_session_error = (
+            hs.config.server.request_token_inhibit_3pid_errors
+        )
 
         self._access_tokens_id_gen = IdGenerator(db_conn, "access_tokens", "id")
         self._refresh_tokens_id_gen = IdGenerator(db_conn, "refresh_tokens", "id")
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index 612914884..0a2589dab 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -676,7 +676,7 @@ async def get_retention_policy_for_room(self, room_id):
         # If the room retention feature is disabled, return a policy with no minimum nor
         # maximum, in order not to filter out events we should filter out when sending to
         # the client.
-        if not self.config.retention_enabled:
+        if not self.config.server.retention_enabled:
             return {"min_lifetime": None, "max_lifetime": None}
 
         def get_retention_policy_for_room_txn(txn):
@@ -700,8 +700,8 @@ def get_retention_policy_for_room_txn(txn):
         # policy.
         if not ret:
             return {
-                "min_lifetime": self.config.retention_default_min_lifetime,
-                "max_lifetime": self.config.retention_default_max_lifetime,
+                "min_lifetime": self.config.server.retention_default_min_lifetime,
+                "max_lifetime": self.config.server.retention_default_max_lifetime,
             }
 
         row = ret[0]
@@ -711,10 +711,10 @@ def get_retention_policy_for_room_txn(txn):
         # The default values will be None if no default policy has been defined, or if one
         # of the attributes is missing from the default policy.
         if row["min_lifetime"] is None:
-            row["min_lifetime"] = self.config.retention_default_min_lifetime
+            row["min_lifetime"] = self.config.server.retention_default_min_lifetime
 
         if row["max_lifetime"] is None:
-            row["max_lifetime"] = self.config.retention_default_max_lifetime
+            row["max_lifetime"] = self.config.server.retention_default_max_lifetime
 
         return row
 
diff --git a/synapse/storage/databases/main/room_batch.py b/synapse/storage/databases/main/room_batch.py
index a38338875..300a563c9 100644
--- a/synapse/storage/databases/main/room_batch.py
+++ b/synapse/storage/databases/main/room_batch.py
@@ -18,7 +18,9 @@
 
 
 class RoomBatchStore(SQLBaseStore):
-    async def get_insertion_event_by_batch_id(self, batch_id: str) -> Optional[str]:
+    async def get_insertion_event_by_batch_id(
+        self, room_id: str, batch_id: str
+    ) -> Optional[str]:
         """Retrieve a insertion event ID.
 
         Args:
@@ -30,7 +32,7 @@ async def get_insertion_event_by_batch_id(self, batch_id: str) -> Optional[str]:
         """
         return await self.db_pool.simple_select_one_onecol(
             table="insertion_events",
-            keyvalues={"next_batch_id": batch_id},
+            keyvalues={"room_id": room_id, "next_batch_id": batch_id},
             retcol="event_id",
             allow_none=True,
         )
diff --git a/synapse/storage/databases/main/search.py b/synapse/storage/databases/main/search.py
index 2a1e99e17..c85383c97 100644
--- a/synapse/storage/databases/main/search.py
+++ b/synapse/storage/databases/main/search.py
@@ -51,7 +51,7 @@ def store_search_entries_txn(
             txn:
             entries: entries to be added to the table
         """
-        if not self.hs.config.enable_search:
+        if not self.hs.config.server.enable_search:
             return
         if isinstance(self.database_engine, PostgresEngine):
             sql = (
@@ -105,7 +105,7 @@ class SearchBackgroundUpdateStore(SearchWorkerStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
-        if not hs.config.enable_search:
+        if not hs.config.server.enable_search:
             return
 
         self.db_pool.updates.register_background_update_handler(
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
index 90d65edc4..e98a45b6a 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -26,6 +26,8 @@
     cast,
 )
 
+from synapse.api.errors import StoreError
+
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -40,12 +42,10 @@
 
 logger = logging.getLogger(__name__)
 
-
 TEMP_TABLE = "_temp_populate_user_directory"
 
 
 class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
-
     # How many records do we calculate before sending it to
     # add_users_who_share_private_rooms?
     SHARE_PRIVATE_WORKING_SET = 500
@@ -230,38 +230,49 @@ def _get_next_batch(
             is_in_room = await self.is_host_joined(room_id, self.server_name)
 
             if is_in_room:
-                is_public = await self.is_room_world_readable_or_publicly_joinable(
-                    room_id
-                )
-
                 users_with_profile = await self.get_users_in_room_with_profiles(room_id)
+                # Throw away users excluded from the directory.
+                users_with_profile = {
+                    user_id: profile
+                    for user_id, profile in users_with_profile.items()
+                    if not self.hs.is_mine_id(user_id)
+                    or await self.should_include_local_user_in_dir(user_id)
+                }
 
-                # Update each user in the user directory.
+                # Upsert a user_directory record for each remote user we see.
                 for user_id, profile in users_with_profile.items():
+                    # Local users are processed separately in
+                    # `_populate_user_directory_users`; there we can read from
+                    # the `profiles` table to ensure we don't leak their per-room
+                    # profiles. It also means we write local users to this table
+                    # exactly once, rather than once for every room they're in.
+                    if self.hs.is_mine_id(user_id):
+                        continue
+                    # TODO `users_with_profile` above reads from the `user_directory`
+                    #   table, meaning that `profile` is bespoke to this room.
+                    #   and this leaks remote users' per-room profiles to the user directory.
                     await self.update_profile_in_user_dir(
                         user_id, profile.display_name, profile.avatar_url
                     )
 
-                to_insert = set()
-
+                # Now update the room sharing tables to include this room.
+                is_public = await self.is_room_world_readable_or_publicly_joinable(
+                    room_id
+                )
                 if is_public:
-                    for user_id in users_with_profile:
-                        if self.get_if_app_services_interested_in_user(user_id):
-                            continue
-
-                        to_insert.add(user_id)
-
-                    if to_insert:
-                        await self.add_users_in_public_rooms(room_id, to_insert)
-                        to_insert.clear()
+                    if users_with_profile:
+                        await self.add_users_in_public_rooms(
+                            room_id, users_with_profile.keys()
+                        )
                 else:
+                    to_insert = set()
                     for user_id in users_with_profile:
+                        # We want the set of pairs (L, M) where L and M are
+                        # in `users_with_profile` and L is local.
+                        # Do so by looking for the local user L first.
                         if not self.hs.is_mine_id(user_id):
                             continue
 
-                        if self.get_if_app_services_interested_in_user(user_id):
-                            continue
-
                         for other_user_id in users_with_profile:
                             if user_id == other_user_id:
                                 continue
@@ -349,10 +360,11 @@ def _get_next_batch(txn: LoggingTransaction) -> Optional[List[str]]:
         )
 
         for user_id in users_to_work_on:
-            profile = await self.get_profileinfo(get_localpart_from_id(user_id))
-            await self.update_profile_in_user_dir(
-                user_id, profile.display_name, profile.avatar_url
-            )
+            if await self.should_include_local_user_in_dir(user_id):
+                profile = await self.get_profileinfo(get_localpart_from_id(user_id))
+                await self.update_profile_in_user_dir(
+                    user_id, profile.display_name, profile.avatar_url
+                )
 
             # We've finished processing a user. Delete it from the table.
             await self.db_pool.simple_delete_one(
@@ -369,6 +381,42 @@ def _get_next_batch(txn: LoggingTransaction) -> Optional[List[str]]:
 
         return len(users_to_work_on)
 
+    async def should_include_local_user_in_dir(self, user: str) -> bool:
+        """Certain classes of local user are omitted from the user directory.
+        Is this user one of them?
+        """
+        # We're opting to exclude the appservice sender (user defined by the
+        # `sender_localpart` in the appservice registration) even though
+        # technically it could be DM-able. In the future, this could potentially
+        # be configurable per-appservice whether the appservice sender can be
+        # contacted.
+        if self.get_app_service_by_user_id(user) is not None:
+            return False
+
+        # We're opting to exclude appservice users (anyone matching the user
+        # namespace regex in the appservice registration) even though technically
+        # they could be DM-able. In the future, this could potentially
+        # be configurable per-appservice whether the appservice users can be
+        # contacted.
+        if self.get_if_app_services_interested_in_user(user):
+            # TODO we might want to make this configurable for each app service
+            return False
+
+        # Support users are for diagnostics and should not appear in the user directory.
+        if await self.is_support_user(user):
+            return False
+
+        # Deactivated users aren't contactable, so should not appear in the user directory.
+        try:
+            if await self.get_user_deactivated_status(user):
+                return False
+        except StoreError:
+            # No such user in the users table. No need to do this when calling
+            # is_support_user---that returns False if the user is missing.
+            return False
+
+        return True
+
     async def is_room_world_readable_or_publicly_joinable(self, room_id: str) -> bool:
         """Check if the room is either world_readable or publically joinable"""
 
@@ -527,7 +575,7 @@ async def get_user_in_directory(self, user_id: str) -> Optional[Dict[str, str]]:
             desc="get_user_in_directory",
         )
 
-    async def update_user_directory_stream_pos(self, stream_id: int) -> None:
+    async def update_user_directory_stream_pos(self, stream_id: Optional[int]) -> None:
         await self.db_pool.simple_update_one(
             table="user_directory_stream_pos",
             keyvalues={},
@@ -537,7 +585,6 @@ async def update_user_directory_stream_pos(self, stream_id: int) -> None:
 
 
 class UserDirectoryStore(UserDirectoryBackgroundUpdateStore):
-
     # How many records do we calculate before sending it to
     # add_users_who_share_private_rooms?
     SHARE_PRIVATE_WORKING_SET = 500
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index f31880b8e..11ca47ea2 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -366,7 +366,7 @@ def _upgrade_existing_database(
             + "new for the server to understand"
         )
 
-    # some of the deltas assume that config.server_name is set correctly, so now
+    # some of the deltas assume that server_name is set correctly, so now
     # is a good time to run the sanity check.
     if not is_empty and "main" in databases:
         from synapse.storage.databases.main import check_database_before_upgrade
@@ -487,6 +487,10 @@ def _upgrade_existing_database(
                 spec = importlib.util.spec_from_file_location(
                     module_name, absolute_path
                 )
+                if spec is None:
+                    raise RuntimeError(
+                        f"Could not build a module spec for {module_name} at {absolute_path}"
+                    )
                 module = importlib.util.module_from_spec(spec)
                 spec.loader.exec_module(module)  # type: ignore
 
diff --git a/synapse/storage/schema/__init__.py b/synapse/storage/schema/__init__.py
index 573e05a48..1aee741a8 100644
--- a/synapse/storage/schema/__init__.py
+++ b/synapse/storage/schema/__init__.py
@@ -12,9 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# When updating these values, please leave a short summary of the changes below.
-
-SCHEMA_VERSION = 64
+SCHEMA_VERSION = 64  # remember to update the list below when updating
 """Represents the expectations made by the codebase about the database schema
 
 This should be incremented whenever the codebase changes its requirements on the
@@ -46,7 +44,7 @@
 """
 
 
-SCHEMA_COMPAT_VERSION = 59
+SCHEMA_COMPAT_VERSION = 60  # 60: "outlier" not in internal_metadata.
 """Limit on how far the synapse codebase can be rolled back without breaking db compat
 
 This value is stored in the database, and checked on startup. If the value in the
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 5e86befde..b5ba1560d 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -15,9 +15,11 @@
 from typing import (
     TYPE_CHECKING,
     Awaitable,
+    Collection,
     Dict,
     Iterable,
     List,
+    Mapping,
     Optional,
     Set,
     Tuple,
@@ -29,7 +31,7 @@
 
 from synapse.api.constants import EventTypes
 from synapse.events import EventBase
-from synapse.types import MutableStateMap, StateMap
+from synapse.types import MutableStateMap, StateKey, StateMap
 
 if TYPE_CHECKING:
     from typing import FrozenSet  # noqa: used within quoted type hint; flake8 sad
@@ -134,6 +136,23 @@ def from_lazy_load_member_list(members: Iterable[str]) -> "StateFilter":
             include_others=True,
         )
 
+    @staticmethod
+    def freeze(types: Mapping[str, Optional[Collection[str]]], include_others: bool):
+        """
+        Returns a (frozen) StateFilter with the same contents as the parameters
+        specified here, which can be made of mutable types.
+        """
+        types_with_frozen_values: Dict[str, Optional[FrozenSet[str]]] = {}
+        for state_types, state_keys in types.items():
+            if state_keys is not None:
+                types_with_frozen_values[state_types] = frozenset(state_keys)
+            else:
+                types_with_frozen_values[state_types] = None
+
+        return StateFilter(
+            frozendict(types_with_frozen_values), include_others=include_others
+        )
+
     def return_expanded(self) -> "StateFilter":
         """Creates a new StateFilter where type wild cards have been removed
         (except for memberships). The returned filter is a superset of the
@@ -356,6 +375,157 @@ def get_member_split(self) -> Tuple["StateFilter", "StateFilter"]:
 
         return member_filter, non_member_filter
 
+    def _decompose_into_four_parts(
+        self,
+    ) -> Tuple[Tuple[bool, Set[str]], Tuple[Set[str], Set[StateKey]]]:
+        """
+        Decomposes this state filter into 4 constituent parts, which can be
+        thought of as this:
+            all? - minus_wildcards + plus_wildcards + plus_state_keys
+
+        where
+        * all represents ALL state
+        * minus_wildcards represents entire state types to remove
+        * plus_wildcards represents entire state types to add
+        * plus_state_keys represents individual state keys to add
+
+        See `recompose_from_four_parts` for the other direction of this
+        correspondence.
+        """
+        is_all = self.include_others
+        excluded_types: Set[str] = {t for t in self.types if is_all}
+        wildcard_types: Set[str] = {t for t, s in self.types.items() if s is None}
+        concrete_keys: Set[StateKey] = set(self.concrete_types())
+
+        return (is_all, excluded_types), (wildcard_types, concrete_keys)
+
+    @staticmethod
+    def _recompose_from_four_parts(
+        all_part: bool,
+        minus_wildcards: Set[str],
+        plus_wildcards: Set[str],
+        plus_state_keys: Set[StateKey],
+    ) -> "StateFilter":
+        """
+        Recomposes a state filter from 4 parts.
+
+        See `decompose_into_four_parts` (the other direction of this
+        correspondence) for descriptions on each of the parts.
+        """
+
+        # {state type -> set of state keys OR None for wildcard}
+        # (The same structure as that of a StateFilter.)
+        new_types: Dict[str, Optional[Set[str]]] = {}
+
+        # if we start with all, insert the excluded statetypes as empty sets
+        # to prevent them from being included
+        if all_part:
+            new_types.update({state_type: set() for state_type in minus_wildcards})
+
+        # insert the plus wildcards
+        new_types.update({state_type: None for state_type in plus_wildcards})
+
+        # insert the specific state keys
+        for state_type, state_key in plus_state_keys:
+            if state_type in new_types:
+                entry = new_types[state_type]
+                if entry is not None:
+                    entry.add(state_key)
+            elif not all_part:
+                # don't insert if the entire type is already included by
+                # include_others as this would actually shrink the state allowed
+                # by this filter.
+                new_types[state_type] = {state_key}
+
+        return StateFilter.freeze(new_types, include_others=all_part)
+
+    def approx_difference(self, other: "StateFilter") -> "StateFilter":
+        """
+        Returns a state filter which represents `self - other`.
+
+        This is useful for determining what state remains to be pulled out of the
+        database if we want the state included by `self` but already have the state
+        included by `other`.
+
+        The returned state filter
+        - MUST include all state events that are included by this filter (`self`)
+          unless they are included by `other`;
+        - MUST NOT include state events not included by this filter (`self`); and
+        - MAY be an over-approximation: the returned state filter
+          MAY additionally include some state events from `other`.
+
+        This implementation attempts to return the narrowest such state filter.
+        In the case that `self` contains wildcards for state types where
+        `other` contains specific state keys, an approximation must be made:
+        the returned state filter keeps the wildcard, as state filters are not
+        able to express 'all state keys except some given examples'.
+        e.g.
+            StateFilter(m.room.member -> None (wildcard))
+                minus
+            StateFilter(m.room.member -> {'@wombat:example.org'})
+                is approximated as
+            StateFilter(m.room.member -> None (wildcard))
+        """
+
+        # We first transform self and other into an alternative representation:
+        #   - whether or not they include all events to begin with ('all')
+        #   - if so, which event types are excluded? ('excludes')
+        #   - which entire event types to include ('wildcards')
+        #   - which concrete state keys to include ('concrete state keys')
+        (self_all, self_excludes), (
+            self_wildcards,
+            self_concrete_keys,
+        ) = self._decompose_into_four_parts()
+        (other_all, other_excludes), (
+            other_wildcards,
+            other_concrete_keys,
+        ) = other._decompose_into_four_parts()
+
+        # Start with an estimate of the difference based on self
+        new_all = self_all
+        # Wildcards from the other can be added to the exclusion filter
+        new_excludes = self_excludes | other_wildcards
+        # We remove wildcards that appeared as wildcards in the other
+        new_wildcards = self_wildcards - other_wildcards
+        # We filter out the concrete state keys that appear in the other
+        # as wildcards or concrete state keys.
+        new_concrete_keys = {
+            (state_type, state_key)
+            for (state_type, state_key) in self_concrete_keys
+            if state_type not in other_wildcards
+        } - other_concrete_keys
+
+        if other_all:
+            if self_all:
+                # If self starts with all, then we add as wildcards any
+                # types which appear in the other's exclusion filter (but
+                # aren't in the self exclusion filter). This is as the other
+                # filter will return everything BUT the types in its exclusion, so
+                # we need to add those excluded types that also match the self
+                # filter as wildcard types in the new filter.
+                new_wildcards |= other_excludes.difference(self_excludes)
+
+            # If other is an `include_others` then the difference isn't.
+            new_all = False
+            # (We have no need for excludes when we don't start with all, as there
+            #  is nothing to exclude.)
+            new_excludes = set()
+
+            # We also filter out all state types that aren't in the exclusion
+            # list of the other.
+            new_wildcards &= other_excludes
+            new_concrete_keys = {
+                (state_type, state_key)
+                for (state_type, state_key) in new_concrete_keys
+                if state_type in other_excludes
+            }
+
+        # Transform our newly-constructed state filter from the alternative
+        # representation back into the normal StateFilter representation.
+        return StateFilter._recompose_from_four_parts(
+            new_all, new_excludes, new_wildcards, new_concrete_keys
+        )
+
 
 class StateGroupStorage:
     """High level interface to fetching state for event."""
diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index 6f7cbe40f..670811611 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -16,42 +16,62 @@
 import threading
 from collections import OrderedDict
 from contextlib import contextmanager
-from typing import Dict, Iterable, List, Optional, Set, Tuple, Union
+from types import TracebackType
+from typing import (
+    AsyncContextManager,
+    ContextManager,
+    Dict,
+    Generator,
+    Generic,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Set,
+    Tuple,
+    Type,
+    TypeVar,
+    Union,
+    cast,
+)
 
 import attr
-from sortedcontainers import SortedSet
+from sortedcontainers import SortedList, SortedSet
 
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.storage.database import DatabasePool, LoggingTransaction
+from synapse.storage.database import (
+    DatabasePool,
+    LoggingDatabaseConnection,
+    LoggingTransaction,
+)
 from synapse.storage.types import Cursor
 from synapse.storage.util.sequence import PostgresSequenceGenerator
 
 logger = logging.getLogger(__name__)
 
 
+T = TypeVar("T")
+
+
 class IdGenerator:
-    def __init__(self, db_conn, table, column):
+    def __init__(
+        self,
+        db_conn: LoggingDatabaseConnection,
+        table: str,
+        column: str,
+    ):
         self._lock = threading.Lock()
         self._next_id = _load_current_id(db_conn, table, column)
 
-    def get_next(self):
+    def get_next(self) -> int:
         with self._lock:
             self._next_id += 1
             return self._next_id
 
 
-def _load_current_id(db_conn, table, column, step=1):
-    """
-
-    Args:
-        db_conn (object):
-        table (str):
-        column (str):
-        step (int):
-
-    Returns:
-        int
-    """
+def _load_current_id(
+    db_conn: LoggingDatabaseConnection, table: str, column: str, step: int = 1
+) -> int:
     # debug logging for https://github.com/matrix-org/synapse/issues/7968
     logger.info("initialising stream generator for %s(%s)", table, column)
     cur = db_conn.cursor(txn_name="_load_current_id")
@@ -59,7 +79,9 @@ def _load_current_id(db_conn, table, column, step=1):
         cur.execute("SELECT MAX(%s) FROM %s" % (column, table))
     else:
         cur.execute("SELECT MIN(%s) FROM %s" % (column, table))
-    (val,) = cur.fetchone()
+    result = cur.fetchone()
+    assert result is not None
+    (val,) = result
     cur.close()
     current_id = int(val) if val else step
     return (max if step > 0 else min)(current_id, step)
@@ -93,16 +115,16 @@ class StreamIdGenerator:
 
     def __init__(
         self,
-        db_conn,
-        table,
-        column,
+        db_conn: LoggingDatabaseConnection,
+        table: str,
+        column: str,
         extra_tables: Iterable[Tuple[str, str]] = (),
-        step=1,
-    ):
+        step: int = 1,
+    ) -> None:
         assert step != 0
         self._lock = threading.Lock()
-        self._step = step
-        self._current = _load_current_id(db_conn, table, column, step)
+        self._step: int = step
+        self._current: int = _load_current_id(db_conn, table, column, step)
         for table, column in extra_tables:
             self._current = (max if step > 0 else min)(
                 self._current, _load_current_id(db_conn, table, column, step)
@@ -115,7 +137,7 @@ def __init__(
         # The key and values are the same, but we never look at the values.
         self._unfinished_ids: OrderedDict[int, int] = OrderedDict()
 
-    def get_next(self):
+    def get_next(self) -> AsyncContextManager[int]:
         """
         Usage:
             async with stream_id_gen.get_next() as stream_id:
@@ -128,7 +150,7 @@ def get_next(self):
             self._unfinished_ids[next_id] = next_id
 
         @contextmanager
-        def manager():
+        def manager() -> Generator[int, None, None]:
             try:
                 yield next_id
             finally:
@@ -137,7 +159,7 @@ def manager():
 
         return _AsyncCtxManagerWrapper(manager())
 
-    def get_next_mult(self, n):
+    def get_next_mult(self, n: int) -> AsyncContextManager[Sequence[int]]:
         """
         Usage:
             async with stream_id_gen.get_next(n) as stream_ids:
@@ -155,7 +177,7 @@ def get_next_mult(self, n):
                 self._unfinished_ids[next_id] = next_id
 
         @contextmanager
-        def manager():
+        def manager() -> Generator[Sequence[int], None, None]:
             try:
                 yield next_ids
             finally:
@@ -215,7 +237,7 @@ class MultiWriterIdGenerator:
 
     def __init__(
         self,
-        db_conn,
+        db_conn: LoggingDatabaseConnection,
         db: DatabasePool,
         stream_name: str,
         instance_name: str,
@@ -223,7 +245,7 @@ def __init__(
         sequence_name: str,
         writers: List[str],
         positive: bool = True,
-    ):
+    ) -> None:
         self._db = db
         self._stream_name = stream_name
         self._instance_name = instance_name
@@ -243,6 +265,15 @@ def __init__(
         # should be less than the minimum of this set (if not empty).
         self._unfinished_ids: SortedSet[int] = SortedSet()
 
+        # We also need to track when we've requested some new stream IDs but
+        # they haven't yet been added to the `_unfinished_ids` set. Every time
+        # we request a new stream ID we add the current max stream ID to the
+        # list, and remove it once we've added the newly allocated IDs to the
+        # `_unfinished_ids` set. This means that we *may* be allocated stream
+        # IDs above those in the list, and so we can't advance the local current
+        # position beyond the minimum stream ID in this list.
+        self._in_flight_fetches: SortedList[int] = SortedList()
+
         # Set of local IDs that we've processed that are larger than the current
         # position, due to there being smaller unpersisted IDs.
         self._finished_ids: Set[int] = set()
@@ -268,6 +299,9 @@ def __init__(
         )
         self._known_persisted_positions: List[int] = []
 
+        # The maximum stream ID that we have seen been allocated across any writer.
+        self._max_seen_allocated_stream_id = 1
+
         self._sequence_gen = PostgresSequenceGenerator(sequence_name)
 
         # We check that the table and sequence haven't diverged.
@@ -283,11 +317,15 @@ def __init__(
         # This goes and fills out the above state from the database.
         self._load_current_ids(db_conn, tables)
 
+        self._max_seen_allocated_stream_id = max(
+            self._current_positions.values(), default=1
+        )
+
     def _load_current_ids(
         self,
-        db_conn,
+        db_conn: LoggingDatabaseConnection,
         tables: List[Tuple[str, str, str]],
-    ):
+    ) -> None:
         cur = db_conn.cursor(txn_name="_load_current_ids")
 
         # Load the current positions of all writers for the stream.
@@ -335,7 +373,9 @@ def _load_current_ids(
                     "agg": "MAX" if self._positive else "-MIN",
                 }
                 cur.execute(sql)
-                (stream_id,) = cur.fetchone()
+                result = cur.fetchone()
+                assert result is not None
+                (stream_id,) = result
 
                 max_stream_id = max(max_stream_id, stream_id)
 
@@ -354,7 +394,7 @@ def _load_current_ids(
 
             self._persisted_upto_position = min_stream_id
 
-            rows = []
+            rows: List[Tuple[str, int]] = []
             for table, instance_column, id_column in tables:
                 sql = """
                     SELECT %(instance)s, %(id)s FROM %(table)s
@@ -367,7 +407,8 @@ def _load_current_ids(
                 }
                 cur.execute(sql, (min_stream_id * self._return_factor,))
 
-                rows.extend(cur)
+                # Cast safety: this corresponds to the types returned by the query above.
+                rows.extend(cast(Iterable[Tuple[str, int]], cur))
 
             # Sort so that we handle rows in order for each instance.
             rows.sort()
@@ -385,13 +426,35 @@ def _load_current_ids(
 
         cur.close()
 
-    def _load_next_id_txn(self, txn) -> int:
-        return self._sequence_gen.get_next_id_txn(txn)
+    def _load_next_id_txn(self, txn: Cursor) -> int:
+        stream_ids = self._load_next_mult_id_txn(txn, 1)
+        return stream_ids[0]
 
-    def _load_next_mult_id_txn(self, txn, n: int) -> List[int]:
-        return self._sequence_gen.get_next_mult_txn(txn, n)
+    def _load_next_mult_id_txn(self, txn: Cursor, n: int) -> List[int]:
+        # We need to track that we've requested some more stream IDs, and what
+        # the current max allocated stream ID is. This is to prevent a race
+        # where we've been allocated stream IDs but they have not yet been added
+        # to the `_unfinished_ids` set, allowing the current position to advance
+        # past them.
+        with self._lock:
+            current_max = self._max_seen_allocated_stream_id
+            self._in_flight_fetches.add(current_max)
+
+        try:
+            stream_ids = self._sequence_gen.get_next_mult_txn(txn, n)
+
+            with self._lock:
+                self._unfinished_ids.update(stream_ids)
+                self._max_seen_allocated_stream_id = max(
+                    self._max_seen_allocated_stream_id, self._unfinished_ids[-1]
+                )
+        finally:
+            with self._lock:
+                self._in_flight_fetches.remove(current_max)
+
+        return stream_ids
 
-    def get_next(self):
+    def get_next(self) -> AsyncContextManager[int]:
         """
         Usage:
             async with stream_id_gen.get_next() as stream_id:
@@ -403,9 +466,12 @@ def get_next(self):
         if self._writers and self._instance_name not in self._writers:
             raise Exception("Tried to allocate stream ID on non-writer")
 
-        return _MultiWriterCtxManager(self)
+        # Cast safety: the second argument to _MultiWriterCtxManager, multiple_ids,
+        # controls the return type. If `None` or omitted, the context manager yields
+        # a single integer stream_id; otherwise it yields a list of stream_ids.
+        return cast(AsyncContextManager[int], _MultiWriterCtxManager(self))
 
-    def get_next_mult(self, n: int):
+    def get_next_mult(self, n: int) -> AsyncContextManager[List[int]]:
         """
         Usage:
             async with stream_id_gen.get_next_mult(5) as stream_ids:
@@ -417,9 +483,10 @@ def get_next_mult(self, n: int):
         if self._writers and self._instance_name not in self._writers:
             raise Exception("Tried to allocate stream ID on non-writer")
 
-        return _MultiWriterCtxManager(self, n)
+        # Cast safety: see get_next.
+        return cast(AsyncContextManager[List[int]], _MultiWriterCtxManager(self, n))
 
-    def get_next_txn(self, txn: LoggingTransaction):
+    def get_next_txn(self, txn: LoggingTransaction) -> int:
         """
         Usage:
 
@@ -434,9 +501,6 @@ def get_next_txn(self, txn: LoggingTransaction):
 
         next_id = self._load_next_id_txn(txn)
 
-        with self._lock:
-            self._unfinished_ids.add(next_id)
-
         txn.call_after(self._mark_id_as_finished, next_id)
         txn.call_on_exception(self._mark_id_as_finished, next_id)
 
@@ -457,7 +521,7 @@ def get_next_txn(self, txn: LoggingTransaction):
 
         return self._return_factor * next_id
 
-    def _mark_id_as_finished(self, next_id: int):
+    def _mark_id_as_finished(self, next_id: int) -> None:
         """The ID has finished being processed so we should advance the
         current position if possible.
         """
@@ -468,15 +532,27 @@ def _mark_id_as_finished(self, next_id: int):
 
             new_cur: Optional[int] = None
 
-            if self._unfinished_ids:
+            if self._unfinished_ids or self._in_flight_fetches:
                 # If there are unfinished IDs then the new position will be the
-                # largest finished ID less than the minimum unfinished ID.
+                # largest finished ID strictly less than the minimum unfinished
+                # ID.
+
+                # The minimum unfinished ID needs to take account of both
+                # `_unfinished_ids` and `_in_flight_fetches`.
+                if self._unfinished_ids and self._in_flight_fetches:
+                    # `_in_flight_fetches` stores the maximum safe stream ID, so
+                    # we add one to make it equivalent to the minimum unsafe ID.
+                    min_unfinished = min(
+                        self._unfinished_ids[0], self._in_flight_fetches[0] + 1
+                    )
+                elif self._in_flight_fetches:
+                    min_unfinished = self._in_flight_fetches[0] + 1
+                else:
+                    min_unfinished = self._unfinished_ids[0]
 
                 finished = set()
-
-                min_unfinshed = self._unfinished_ids[0]
                 for s in self._finished_ids:
-                    if s < min_unfinshed:
+                    if s < min_unfinished:
                         if new_cur is None or new_cur < s:
                             new_cur = s
                     else:
@@ -534,7 +610,7 @@ def get_positions(self) -> Dict[str, int]:
                 for name, i in self._current_positions.items()
             }
 
-    def advance(self, instance_name: str, new_id: int):
+    def advance(self, instance_name: str, new_id: int) -> None:
         """Advance the position of the named writer to the given ID, if greater
         than existing entry.
         """
@@ -546,6 +622,10 @@ def advance(self, instance_name: str, new_id: int):
                 new_id, self._current_positions.get(instance_name, 0)
             )
 
+            self._max_seen_allocated_stream_id = max(
+                self._max_seen_allocated_stream_id, new_id
+            )
+
             self._add_persisted_position(new_id)
 
     def get_persisted_upto_position(self) -> int:
@@ -560,7 +640,7 @@ def get_persisted_upto_position(self) -> int:
         with self._lock:
             return self._return_factor * self._persisted_upto_position
 
-    def _add_persisted_position(self, new_id: int):
+    def _add_persisted_position(self, new_id: int) -> None:
         """Record that we have persisted a position.
 
         This is used to keep the `_current_positions` up to date.
@@ -576,7 +656,11 @@ def _add_persisted_position(self, new_id: int):
         # to report a recent position when asked, rather than a potentially old
         # one (if this instance hasn't written anything for a while).
         our_current_position = self._current_positions.get(self._instance_name)
-        if our_current_position and not self._unfinished_ids:
+        if (
+            our_current_position
+            and not self._unfinished_ids
+            and not self._in_flight_fetches
+        ):
             self._current_positions[self._instance_name] = max(
                 our_current_position, new_id
             )
@@ -606,7 +690,7 @@ def _add_persisted_position(self, new_id: int):
                 # do.
                 break
 
-    def _update_stream_positions_table_txn(self, txn: Cursor):
+    def _update_stream_positions_table_txn(self, txn: Cursor) -> None:
         """Update the `stream_positions` table with newly persisted position."""
 
         if not self._writers:
@@ -628,20 +712,25 @@ def _update_stream_positions_table_txn(self, txn: Cursor):
         txn.execute(sql, (self._stream_name, self._instance_name, pos))
 
 
-@attr.s(slots=True)
-class _AsyncCtxManagerWrapper:
+@attr.s(frozen=True, auto_attribs=True)
+class _AsyncCtxManagerWrapper(Generic[T]):
     """Helper class to convert a plain context manager to an async one.
 
     This is mainly useful if you have a plain context manager but the interface
     requires an async one.
     """
 
-    inner = attr.ib()
+    inner: ContextManager[T]
 
-    async def __aenter__(self):
+    async def __aenter__(self) -> T:
         return self.inner.__enter__()
 
-    async def __aexit__(self, exc_type, exc, tb):
+    async def __aexit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc: Optional[BaseException],
+        tb: Optional[TracebackType],
+    ) -> Optional[bool]:
         return self.inner.__exit__(exc_type, exc, tb)
 
 
@@ -663,15 +752,17 @@ async def __aenter__(self) -> Union[int, List[int]]:
             db_autocommit=True,
         )
 
-        with self.id_gen._lock:
-            self.id_gen._unfinished_ids.update(self.stream_ids)
-
         if self.multiple_ids is None:
             return self.stream_ids[0] * self.id_gen._return_factor
         else:
             return [i * self.id_gen._return_factor for i in self.stream_ids]
 
-    async def __aexit__(self, exc_type, exc, tb):
+    async def __aexit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc: Optional[BaseException],
+        tb: Optional[TracebackType],
+    ) -> bool:
         for i in self.stream_ids:
             self.id_gen._mark_id_as_finished(i)
 
diff --git a/synapse/storage/util/sequence.py b/synapse/storage/util/sequence.py
index bb33e04fb..75268cbe1 100644
--- a/synapse/storage/util/sequence.py
+++ b/synapse/storage/util/sequence.py
@@ -81,7 +81,7 @@ def check_consistency(
         id_column: str,
         stream_name: Optional[str] = None,
         positive: bool = True,
-    ):
+    ) -> None:
         """Should be called during start up to test that the current value of
         the sequence is greater than or equal to the maximum ID in the table.
 
@@ -122,7 +122,7 @@ def check_consistency(
         id_column: str,
         stream_name: Optional[str] = None,
         positive: bool = True,
-    ):
+    ) -> None:
         """See SequenceGenerator.check_consistency for docstring."""
 
         txn = db_conn.cursor(txn_name="sequence.check_consistency")
@@ -244,7 +244,7 @@ def check_consistency(
         id_column: str,
         stream_name: Optional[str] = None,
         positive: bool = True,
-    ):
+    ) -> None:
         # There is nothing to do for in memory sequences
         pass
 
diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index bd234549b..abf53d149 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -50,7 +50,16 @@ def _handle_frozendict(obj: Any) -> Dict[Any, Any]:
     if type(obj) is frozendict:
         # fishing the protected dict out of the object is a bit nasty,
         # but we don't really want the overhead of copying the dict.
-        return obj._dict
+        try:
+            # Safety: we catch the AttributeError immediately below.
+            # See https://github.com/matrix-org/python-canonicaljson/issues/36#issuecomment-927816293
+            # for discussion on how frozendict's internals have changed over time.
+            return obj._dict  # type: ignore[attr-defined]
+        except AttributeError:
+            # When the C implementation of frozendict is used,
+            # there isn't a `_dict` attribute with a dict
+            # so we resort to making a copy of the frozendict
+            return dict(obj)
     raise TypeError(
         "Object of type %s is not JSON serializable" % obj.__class__.__name__
     )
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 82d918a05..5df80ea8e 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -438,7 +438,8 @@ def _ctx_manager():
             try:
                 yield
             finally:
-                new_defer.callback(None)
+                with PreserveLoggingContext():
+                    new_defer.callback(None)
                 self.key_to_current_readers.get(key, set()).discard(new_defer)
 
         return _ctx_manager()
@@ -466,7 +467,8 @@ def _ctx_manager():
             try:
                 yield
             finally:
-                new_defer.callback(None)
+                with PreserveLoggingContext():
+                    new_defer.callback(None)
                 if self.key_to_current_writer[key] == new_defer:
                     self.key_to_current_writer.pop(key)
 
diff --git a/synapse/util/caches/cached_call.py b/synapse/util/caches/cached_call.py
index e58dd91ed..470f4f91a 100644
--- a/synapse/util/caches/cached_call.py
+++ b/synapse/util/caches/cached_call.py
@@ -85,7 +85,7 @@ async def get(self) -> TV:
             # result in the deferred, since `awaiting` a deferred destroys its result.
             # (Also, if it's a Failure, GCing the deferred would log a critical error
             # about unhandled Failures)
-            def got_result(r):
+            def got_result(r: Union[TV, Failure]) -> None:
                 self._result = r
 
             self._deferred.addBoth(got_result)
diff --git a/synapse/util/caches/deferred_cache.py b/synapse/util/caches/deferred_cache.py
index 6262efe07..da502aec1 100644
--- a/synapse/util/caches/deferred_cache.py
+++ b/synapse/util/caches/deferred_cache.py
@@ -31,6 +31,7 @@
 
 from twisted.internet import defer
 from twisted.python import failure
+from twisted.python.failure import Failure
 
 from synapse.util.async_helpers import ObservableDeferred
 from synapse.util.caches.lrucache import LruCache
@@ -112,7 +113,7 @@ def metrics_cb() -> None:
         self.thread: Optional[threading.Thread] = None
 
     @property
-    def max_entries(self):
+    def max_entries(self) -> int:
         return self.cache.max_size
 
     def check_thread(self) -> None:
@@ -258,7 +259,7 @@ def compare_and_pop() -> bool:
 
             return False
 
-        def cb(result) -> None:
+        def cb(result: VT) -> None:
             if compare_and_pop():
                 self.cache.set(key, result, entry.callbacks)
             else:
@@ -270,7 +271,7 @@ def cb(result) -> None:
                 # not have been. Either way, let's double-check now.
                 entry.invalidate()
 
-        def eb(_fail) -> None:
+        def eb(_fail: Failure) -> None:
             compare_and_pop()
             entry.invalidate()
 
@@ -284,11 +285,11 @@ def eb(_fail) -> None:
 
     def prefill(
         self, key: KT, value: VT, callback: Optional[Callable[[], None]] = None
-    ):
+    ) -> None:
         callbacks = [callback] if callback else []
         self.cache.set(key, value, callbacks=callbacks)
 
-    def invalidate(self, key):
+    def invalidate(self, key) -> None:
         """Delete a key, or tree of entries
 
         If the cache is backed by a regular dict, then "key" must be of
diff --git a/synapse/util/caches/lrucache.py b/synapse/util/caches/lrucache.py
index 4ff62b403..a0a7a9de3 100644
--- a/synapse/util/caches/lrucache.py
+++ b/synapse/util/caches/lrucache.py
@@ -52,7 +52,7 @@
 try:
     from pympler.asizeof import Asizer
 
-    def _get_size_of(val: Any, *, recurse=True) -> int:
+    def _get_size_of(val: Any, *, recurse: bool = True) -> int:
         """Get an estimate of the size in bytes of the object.
 
         Args:
@@ -71,7 +71,7 @@ def _get_size_of(val: Any, *, recurse=True) -> int:
 
 except ImportError:
 
-    def _get_size_of(val: Any, *, recurse=True) -> int:
+    def _get_size_of(val: Any, *, recurse: bool = True) -> int:
         return 0
 
 
@@ -85,15 +85,6 @@ def _get_size_of(val: Any, *, recurse=True) -> int:
 # a general type var, distinct from either KT or VT
 T = TypeVar("T")
 
-
-def enumerate_leaves(node, depth):
-    if depth == 0:
-        yield node
-    else:
-        for n in node.values():
-            yield from enumerate_leaves(n, depth - 1)
-
-
 P = TypeVar("P")
 
 
@@ -102,7 +93,7 @@ class _TimedListNode(ListNode[P]):
 
     __slots__ = ["last_access_ts_secs"]
 
-    def update_last_access(self, clock: Clock):
+    def update_last_access(self, clock: Clock) -> None:
         self.last_access_ts_secs = int(clock.time())
 
 
@@ -115,7 +106,7 @@ def update_last_access(self, clock: Clock):
 
 
 @wrap_as_background_process("LruCache._expire_old_entries")
-async def _expire_old_entries(clock: Clock, expiry_seconds: int):
+async def _expire_old_entries(clock: Clock, expiry_seconds: int) -> None:
     """Walks the global cache list to find cache entries that haven't been
     accessed in the given number of seconds.
     """
@@ -163,7 +154,7 @@ async def _expire_old_entries(clock: Clock, expiry_seconds: int):
     logger.info("Dropped %d items from caches", i)
 
 
-def setup_expire_lru_cache_entries(hs: "HomeServer"):
+def setup_expire_lru_cache_entries(hs: "HomeServer") -> None:
     """Start a background job that expires all cache entries if they have not
     been accessed for the given number of seconds.
     """
@@ -183,7 +174,7 @@ def setup_expire_lru_cache_entries(hs: "HomeServer"):
     )
 
 
-class _Node:
+class _Node(Generic[KT, VT]):
     __slots__ = [
         "_list_node",
         "_global_list_node",
@@ -197,8 +188,8 @@ class _Node:
     def __init__(
         self,
         root: "ListNode[_Node]",
-        key,
-        value,
+        key: KT,
+        value: VT,
         cache: "weakref.ReferenceType[LruCache]",
         clock: Clock,
         callbacks: Collection[Callable[[], None]] = (),
@@ -409,7 +400,7 @@ def evict() -> None:
 
         def synchronized(f: FT) -> FT:
             @wraps(f)
-            def inner(*args, **kwargs):
+            def inner(*args: Any, **kwargs: Any) -> Any:
                 with lock:
                     return f(*args, **kwargs)
 
@@ -418,17 +409,19 @@ def inner(*args, **kwargs):
         cached_cache_len = [0]
         if size_callback is not None:
 
-            def cache_len():
+            def cache_len() -> int:
                 return cached_cache_len[0]
 
         else:
 
-            def cache_len():
+            def cache_len() -> int:
                 return len(cache)
 
         self.len = synchronized(cache_len)
 
-        def add_node(key, value, callbacks: Collection[Callable[[], None]] = ()):
+        def add_node(
+            key: KT, value: VT, callbacks: Collection[Callable[[], None]] = ()
+        ) -> None:
             node = _Node(
                 list_root,
                 key,
@@ -446,7 +439,7 @@ def add_node(key, value, callbacks: Collection[Callable[[], None]] = ()):
             if caches.TRACK_MEMORY_USAGE and metrics:
                 metrics.inc_memory_usage(node.memory)
 
-        def move_node_to_front(node: _Node):
+        def move_node_to_front(node: _Node) -> None:
             node.move_to_front(real_clock, list_root)
 
         def delete_node(node: _Node) -> int:
@@ -488,7 +481,7 @@ def cache_get(
             default: Optional[T] = None,
             callbacks: Collection[Callable[[], None]] = (),
             update_metrics: bool = True,
-        ):
+        ) -> Union[None, T, VT]:
             node = cache.get(key, None)
             if node is not None:
                 move_node_to_front(node)
@@ -502,7 +495,9 @@ def cache_get(
                 return default
 
         @synchronized
-        def cache_set(key: KT, value: VT, callbacks: Iterable[Callable[[], None]] = ()):
+        def cache_set(
+            key: KT, value: VT, callbacks: Iterable[Callable[[], None]] = ()
+        ) -> None:
             node = cache.get(key, None)
             if node is not None:
                 # We sometimes store large objects, e.g. dicts, which cause
@@ -547,7 +542,7 @@ def cache_pop(key: KT, default: T) -> Union[T, VT]:
             ...
 
         @synchronized
-        def cache_pop(key: KT, default: Optional[T] = None):
+        def cache_pop(key: KT, default: Optional[T] = None) -> Union[None, T, VT]:
             node = cache.get(key, None)
             if node:
                 delete_node(node)
@@ -612,25 +607,25 @@ def cache_contains(key: KT) -> bool:
         self.contains = cache_contains
         self.clear = cache_clear
 
-    def __getitem__(self, key):
+    def __getitem__(self, key: KT) -> VT:
         result = self.get(key, self.sentinel)
         if result is self.sentinel:
             raise KeyError()
         else:
-            return result
+            return cast(VT, result)
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key: KT, value: VT) -> None:
         self.set(key, value)
 
-    def __delitem__(self, key, value):
+    def __delitem__(self, key: KT, value: VT) -> None:
         result = self.pop(key, self.sentinel)
         if result is self.sentinel:
             raise KeyError()
 
-    def __len__(self):
+    def __len__(self) -> int:
         return self.len()
 
-    def __contains__(self, key):
+    def __contains__(self, key: KT) -> bool:
         return self.contains(key)
 
     def set_cache_factor(self, factor: float) -> bool:
diff --git a/synapse/util/caches/response_cache.py b/synapse/util/caches/response_cache.py
index ed7204336..88ccf4433 100644
--- a/synapse/util/caches/response_cache.py
+++ b/synapse/util/caches/response_cache.py
@@ -104,8 +104,8 @@ def get(self, key: KV) -> Optional[defer.Deferred]:
             return None
 
     def _set(
-        self, context: ResponseCacheContext[KV], deferred: defer.Deferred
-    ) -> defer.Deferred:
+        self, context: ResponseCacheContext[KV], deferred: "defer.Deferred[RV]"
+    ) -> "defer.Deferred[RV]":
         """Set the entry for the given key to the given deferred.
 
         *deferred* should run its callbacks in the sentinel logcontext (ie,
@@ -126,7 +126,7 @@ def _set(
         key = context.cache_key
         self.pending_result_cache[key] = result
 
-        def on_complete(r):
+        def on_complete(r: RV) -> RV:
             # if this cache has a non-zero timeout, and the callback has not cleared
             # the should_cache bit, we leave it in the cache for now and schedule
             # its removal later.
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py
index 27b1da235..330709b8b 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -40,10 +40,10 @@ def __init__(
         self,
         name: str,
         current_stream_pos: int,
-        max_size=10000,
+        max_size: int = 10000,
         prefilled_cache: Optional[Mapping[EntityType, int]] = None,
-    ):
-        self._original_max_size = max_size
+    ) -> None:
+        self._original_max_size: int = max_size
         self._max_size = math.floor(max_size)
         self._entity_to_key: Dict[EntityType, int] = {}
 
diff --git a/synapse/util/caches/ttlcache.py b/synapse/util/caches/ttlcache.py
index 46afe3f93..0b9ac26b6 100644
--- a/synapse/util/caches/ttlcache.py
+++ b/synapse/util/caches/ttlcache.py
@@ -159,12 +159,12 @@ def expire(self) -> None:
             del self._expiry_list[0]
 
 
-@attr.s(frozen=True, slots=True)
-class _CacheEntry:
+@attr.s(frozen=True, slots=True, auto_attribs=True)
+class _CacheEntry:  # Should be Generic[KT, VT]. See python-attrs/attrs#313
     """TTLCache entry"""
 
     # expiry_time is the first attribute, so that entries are sorted by expiry.
-    expiry_time = attr.ib(type=float)
-    ttl = attr.ib(type=float)
-    key = attr.ib()
-    value = attr.ib()
+    expiry_time: float
+    ttl: float
+    key: Any  # should be KT
+    value: Any  # should be VT
diff --git a/synapse/util/daemonize.py b/synapse/util/daemonize.py
index f1a351cfd..de04f34e4 100644
--- a/synapse/util/daemonize.py
+++ b/synapse/util/daemonize.py
@@ -19,6 +19,8 @@
 import os
 import signal
 import sys
+from types import FrameType, TracebackType
+from typing import NoReturn, Type
 
 
 def daemonize_process(pid_file: str, logger: logging.Logger, chdir: str = "/") -> None:
@@ -97,7 +99,9 @@ def daemonize_process(pid_file: str, logger: logging.Logger, chdir: str = "/") -
     # (we don't normally expect reactor.run to raise any exceptions, but this will
     # also catch any other uncaught exceptions before we get that far.)
 
-    def excepthook(type_, value, traceback):
+    def excepthook(
+        type_: Type[BaseException], value: BaseException, traceback: TracebackType
+    ) -> None:
         logger.critical("Unhanded exception", exc_info=(type_, value, traceback))
 
     sys.excepthook = excepthook
@@ -119,7 +123,7 @@ def excepthook(type_, value, traceback):
         sys.exit(1)
 
     # write a log line on SIGTERM.
-    def sigterm(signum, frame):
+    def sigterm(signum: signal.Signals, frame: FrameType) -> NoReturn:
         logger.warning("Caught signal %s. Stopping daemon." % signum)
         sys.exit(0)
 
diff --git a/synapse/util/metrics.py b/synapse/util/metrics.py
index 1b82dca81..1e784b3f1 100644
--- a/synapse/util/metrics.py
+++ b/synapse/util/metrics.py
@@ -14,9 +14,11 @@
 
 import logging
 from functools import wraps
-from typing import Any, Callable, Optional, TypeVar, cast
+from types import TracebackType
+from typing import Any, Callable, Optional, Type, TypeVar, cast
 
 from prometheus_client import Counter
+from typing_extensions import Protocol
 
 from synapse.logging.context import (
     ContextResourceUsage,
@@ -24,6 +26,7 @@
     current_context,
 )
 from synapse.metrics import InFlightGauge
+from synapse.util import Clock
 
 logger = logging.getLogger(__name__)
 
@@ -64,6 +67,10 @@
 T = TypeVar("T", bound=Callable[..., Any])
 
 
+class HasClock(Protocol):
+    clock: Clock
+
+
 def measure_func(name: Optional[str] = None) -> Callable[[T], T]:
     """
     Used to decorate an async function with a `Measure` context manager.
@@ -86,7 +93,7 @@ def wrapper(func: T) -> T:
         block_name = func.__name__ if name is None else name
 
         @wraps(func)
-        async def measured_func(self, *args, **kwargs):
+        async def measured_func(self: HasClock, *args: Any, **kwargs: Any) -> Any:
             with Measure(self.clock, block_name):
                 r = await func(self, *args, **kwargs)
             return r
@@ -104,10 +111,10 @@ class Measure:
         "start",
     ]
 
-    def __init__(self, clock, name: str):
+    def __init__(self, clock: Clock, name: str) -> None:
         """
         Args:
-            clock: A n object with a "time()" method, which returns the current
+            clock: An object with a "time()" method, which returns the current
                 time in seconds.
             name: The name of the metric to report.
         """
@@ -124,7 +131,7 @@ def __init__(self, clock, name: str):
             assert isinstance(curr_context, LoggingContext)
             parent_context = curr_context
         self._logging_context = LoggingContext(str(curr_context), parent_context)
-        self.start: Optional[int] = None
+        self.start: Optional[float] = None
 
     def __enter__(self) -> "Measure":
         if self.start is not None:
@@ -138,7 +145,12 @@ def __enter__(self) -> "Measure":
 
         return self
 
-    def __exit__(self, exc_type, exc_val, exc_tb):
+    def __exit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        exc_tb: Optional[TracebackType],
+    ) -> None:
         if self.start is None:
             raise RuntimeError("Measure() block exited without being entered")
 
@@ -168,8 +180,9 @@ def get_resource_usage(self) -> ContextResourceUsage:
         """
         return self._logging_context.get_resource_usage()
 
-    def _update_in_flight(self, metrics):
+    def _update_in_flight(self, metrics) -> None:
         """Gets called when processing in flight metrics"""
+        assert self.start is not None
         duration = self.clock.time() - self.start
 
         metrics.real_time_max = max(metrics.real_time_max, duration)
diff --git a/synapse/util/patch_inline_callbacks.py b/synapse/util/patch_inline_callbacks.py
index 9dd010af3..1f18654d4 100644
--- a/synapse/util/patch_inline_callbacks.py
+++ b/synapse/util/patch_inline_callbacks.py
@@ -14,7 +14,7 @@
 
 import functools
 import sys
-from typing import Any, Callable, List
+from typing import Any, Callable, Generator, List, TypeVar
 
 from twisted.internet import defer
 from twisted.internet.defer import Deferred
@@ -24,6 +24,9 @@
 _already_patched = False
 
 
+T = TypeVar("T")
+
+
 def do_patch() -> None:
     """
     Patch defer.inlineCallbacks so that it checks the state of the logcontext on exit
@@ -37,15 +40,19 @@ def do_patch() -> None:
     if _already_patched:
         return
 
-    def new_inline_callbacks(f):
+    def new_inline_callbacks(
+        f: Callable[..., Generator["Deferred[object]", object, T]]
+    ) -> Callable[..., "Deferred[T]"]:
         @functools.wraps(f)
-        def wrapped(*args, **kwargs):
+        def wrapped(*args: Any, **kwargs: Any) -> "Deferred[T]":
             start_context = current_context()
             changes: List[str] = []
-            orig = orig_inline_callbacks(_check_yield_points(f, changes))
+            orig: Callable[..., "Deferred[T]"] = orig_inline_callbacks(
+                _check_yield_points(f, changes)
+            )
 
             try:
-                res = orig(*args, **kwargs)
+                res: "Deferred[T]" = orig(*args, **kwargs)
             except Exception:
                 if current_context() != start_context:
                     for err in changes:
@@ -84,7 +91,7 @@ def wrapped(*args, **kwargs):
                 print(err, file=sys.stderr)
                 raise Exception(err)
 
-            def check_ctx(r):
+            def check_ctx(r: T) -> T:
                 if current_context() != start_context:
                     for err in changes:
                         print(err, file=sys.stderr)
@@ -107,7 +114,10 @@ def check_ctx(r):
     _already_patched = True
 
 
-def _check_yield_points(f: Callable, changes: List[str]) -> Callable:
+def _check_yield_points(
+    f: Callable[..., Generator["Deferred[object]", object, T]],
+    changes: List[str],
+) -> Callable:
     """Wraps a generator that is about to be passed to defer.inlineCallbacks
     checking that after every yield the log contexts are correct.
 
@@ -127,7 +137,9 @@ def _check_yield_points(f: Callable, changes: List[str]) -> Callable:
     from synapse.logging.context import current_context
 
     @functools.wraps(f)
-    def check_yield_points_inner(*args, **kwargs):
+    def check_yield_points_inner(
+        *args: Any, **kwargs: Any
+    ) -> Generator["Deferred[object]", object, T]:
         gen = f(*args, **kwargs)
 
         last_yield_line_no = gen.gi_frame.f_lineno
diff --git a/synapse/util/threepids.py b/synapse/util/threepids.py
index 8877509ee..c7f8437e2 100644
--- a/synapse/util/threepids.py
+++ b/synapse/util/threepids.py
@@ -43,12 +43,11 @@ async def check_3pid_allowed(hs: "HomeServer", medium: str, address: str) -> boo
     Returns:
         bool: whether the 3PID medium/address is allowed to be added to this HS
     """
-
-    if hs.config.check_is_for_allowed_local_3pids:
+    if hs.config.registration.check_is_for_allowed_local_3pids:
         data = await hs.get_simple_http_client().get_json(
             "https://%s%s"
             % (
-                hs.config.check_is_for_allowed_local_3pids,
+                hs.config.registration.check_is_for_allowed_local_3pids,
                 "/_matrix/identity/api/v1/internal-info",
             ),
             {"medium": medium, "address": address},
@@ -60,8 +59,8 @@ async def check_3pid_allowed(hs: "HomeServer", medium: str, address: str) -> boo
 
         # Check if this user is intended to register for this homeserver
         if (
-            data.get("hs") != hs.config.server_name
-            and data.get("shadow_hs") != hs.config.server_name
+            data.get("hs") != hs.config.server.server_name
+            and data.get("shadow_hs") != hs.config.server.server_name
         ):
             return False
 
@@ -71,8 +70,8 @@ async def check_3pid_allowed(hs: "HomeServer", medium: str, address: str) -> boo
 
         return True
 
-    if hs.config.allowed_local_3pids:
-        for constraint in hs.config.allowed_local_3pids:
+    if hs.config.registration.allowed_local_3pids:
+        for constraint in hs.config.registration.allowed_local_3pids:
             logger.debug(
                 "Checking 3PID %s (%s) against %s (%s)",
                 address,
diff --git a/synapse/util/versionstring.py b/synapse/util/versionstring.py
index 1c20b24bb..899ee0adc 100644
--- a/synapse/util/versionstring.py
+++ b/synapse/util/versionstring.py
@@ -15,14 +15,18 @@
 import logging
 import os
 import subprocess
+from types import ModuleType
+from typing import Dict
 
 logger = logging.getLogger(__name__)
 
+version_cache: Dict[ModuleType, str] = {}
 
-def get_version_string(module) -> str:
+
+def get_version_string(module: ModuleType) -> str:
     """Given a module calculate a git-aware version string for it.
 
-    If called on a module not in a git checkout will return `__verison__`.
+    If called on a module not in a git checkout will return `__version__`.
 
     Args:
         module (module)
@@ -31,11 +35,13 @@ def get_version_string(module) -> str:
         str
     """
 
-    cached_version = getattr(module, "_synapse_version_string_cache", None)
-    if cached_version:
+    cached_version = version_cache.get(module)
+    if cached_version is not None:
         return cached_version
 
-    version_string = module.__version__
+    # We want this to fail loudly with an AttributeError. Type-ignore this so
+    # mypy only considers the happy path.
+    version_string = module.__version__  # type: ignore[attr-defined]
 
     try:
         null = open(os.devnull, "w")
@@ -97,10 +103,15 @@ def get_version_string(module) -> str:
                 s for s in (git_branch, git_tag, git_commit, git_dirty) if s
             )
 
-            version_string = "%s (%s)" % (module.__version__, git_version)
+            version_string = "%s (%s)" % (
+                # If the __version__ attribute doesn't exist, we'll have failed
+                # loudly above.
+                module.__version__,  # type: ignore[attr-defined]
+                git_version,
+            )
     except Exception as e:
         logger.info("Failed to check for git repository: %s", e)
 
-    module._synapse_version_string_cache = version_string
+    version_cache[module] = version_string
 
     return version_string
diff --git a/tests/api/test_auth.py b/tests/api/test_auth.py
index cccff7af2..3aa9ba3c4 100644
--- a/tests/api/test_auth.py
+++ b/tests/api/test_auth.py
@@ -217,7 +217,7 @@ def test_get_user_from_macaroon(self):
 
         user_id = "@baldrick:matrix.org"
         macaroon = pymacaroons.Macaroon(
-            location=self.hs.config.server_name,
+            location=self.hs.config.server.server_name,
             identifier="key",
             key=self.hs.config.key.macaroon_secret_key,
         )
@@ -239,7 +239,7 @@ def test_get_guest_user_from_macaroon(self):
 
         user_id = "@baldrick:matrix.org"
         macaroon = pymacaroons.Macaroon(
-            location=self.hs.config.server_name,
+            location=self.hs.config.server.server_name,
             identifier="key",
             key=self.hs.config.key.macaroon_secret_key,
         )
@@ -268,7 +268,7 @@ def test_blocking_mau(self):
         self.store.get_monthly_active_count = simple_async_mock(lots_of_users)
 
         e = self.get_failure(self.auth.check_auth_blocking(), ResourceLimitError)
-        self.assertEquals(e.value.admin_contact, self.hs.config.admin_contact)
+        self.assertEquals(e.value.admin_contact, self.hs.config.server.admin_contact)
         self.assertEquals(e.value.errcode, Codes.RESOURCE_LIMIT_EXCEEDED)
         self.assertEquals(e.value.code, 403)
 
@@ -303,7 +303,7 @@ def test_blocking_mau__appservice_requester_allowed_when_not_tracking_ips(self):
 
         appservice = ApplicationService(
             "abcd",
-            self.hs.config.server_name,
+            self.hs.config.server.server_name,
             id="1234",
             namespaces={
                 "users": [{"regex": "@_appservice.*:sender", "exclusive": True}]
@@ -332,7 +332,7 @@ def test_blocking_mau__appservice_requester_disallowed_when_tracking_ips(self):
 
         appservice = ApplicationService(
             "abcd",
-            self.hs.config.server_name,
+            self.hs.config.server.server_name,
             id="1234",
             namespaces={
                 "users": [{"regex": "@_appservice.*:sender", "exclusive": True}]
@@ -372,7 +372,7 @@ def test_hs_disabled(self):
         self.auth_blocking._hs_disabled = True
         self.auth_blocking._hs_disabled_message = "Reason for being disabled"
         e = self.get_failure(self.auth.check_auth_blocking(), ResourceLimitError)
-        self.assertEquals(e.value.admin_contact, self.hs.config.admin_contact)
+        self.assertEquals(e.value.admin_contact, self.hs.config.server.admin_contact)
         self.assertEquals(e.value.errcode, Codes.RESOURCE_LIMIT_EXCEEDED)
         self.assertEquals(e.value.code, 403)
 
@@ -387,7 +387,7 @@ def test_hs_disabled_no_server_notices_user(self):
         self.auth_blocking._hs_disabled = True
         self.auth_blocking._hs_disabled_message = "Reason for being disabled"
         e = self.get_failure(self.auth.check_auth_blocking(), ResourceLimitError)
-        self.assertEquals(e.value.admin_contact, self.hs.config.admin_contact)
+        self.assertEquals(e.value.admin_contact, self.hs.config.server.admin_contact)
         self.assertEquals(e.value.errcode, Codes.RESOURCE_LIMIT_EXCEEDED)
         self.assertEquals(e.value.code, 403)
 
diff --git a/tests/appservice/test_scheduler.py b/tests/appservice/test_scheduler.py
index a2b5ed203..55f0899ba 100644
--- a/tests/appservice/test_scheduler.py
+++ b/tests/appservice/test_scheduler.py
@@ -24,7 +24,7 @@
 from synapse.logging.context import make_deferred_yieldable
 
 from tests import unittest
-from tests.test_utils import make_awaitable
+from tests.test_utils import simple_async_mock
 
 from ..utils import MockClock
 
@@ -49,11 +49,10 @@ def test_single_service_up_txn_sent(self):
         txn = Mock(id=txn_id, service=service, events=events)
 
         # mock methods
-        self.store.get_appservice_state = Mock(
-            return_value=defer.succeed(ApplicationServiceState.UP)
-        )
-        txn.send = Mock(return_value=make_awaitable(True))
-        self.store.create_appservice_txn = Mock(return_value=defer.succeed(txn))
+        self.store.get_appservice_state = simple_async_mock(ApplicationServiceState.UP)
+        txn.send = simple_async_mock(True)
+        txn.complete = simple_async_mock(True)
+        self.store.create_appservice_txn = simple_async_mock(txn)
 
         # actual call
         self.successResultOf(defer.ensureDeferred(self.txnctrl.send(service, events)))
@@ -71,10 +70,10 @@ def test_single_service_down(self):
         events = [Mock(), Mock()]
 
         txn = Mock(id="idhere", service=service, events=events)
-        self.store.get_appservice_state = Mock(
-            return_value=defer.succeed(ApplicationServiceState.DOWN)
+        self.store.get_appservice_state = simple_async_mock(
+            ApplicationServiceState.DOWN
         )
-        self.store.create_appservice_txn = Mock(return_value=defer.succeed(txn))
+        self.store.create_appservice_txn = simple_async_mock(txn)
 
         # actual call
         self.successResultOf(defer.ensureDeferred(self.txnctrl.send(service, events)))
@@ -94,12 +93,10 @@ def test_single_service_up_txn_not_sent(self):
         txn = Mock(id=txn_id, service=service, events=events)
 
         # mock methods
-        self.store.get_appservice_state = Mock(
-            return_value=defer.succeed(ApplicationServiceState.UP)
-        )
-        self.store.set_appservice_state = Mock(return_value=defer.succeed(True))
-        txn.send = Mock(return_value=make_awaitable(False))  # fails to send
-        self.store.create_appservice_txn = Mock(return_value=defer.succeed(txn))
+        self.store.get_appservice_state = simple_async_mock(ApplicationServiceState.UP)
+        self.store.set_appservice_state = simple_async_mock(True)
+        txn.send = simple_async_mock(False)  # fails to send
+        self.store.create_appservice_txn = simple_async_mock(txn)
 
         # actual call
         self.successResultOf(defer.ensureDeferred(self.txnctrl.send(service, events)))
@@ -122,7 +119,7 @@ def setUp(self):
         self.as_api = Mock()
         self.store = Mock()
         self.service = Mock()
-        self.callback = Mock()
+        self.callback = simple_async_mock()
         self.recoverer = _Recoverer(
             clock=self.clock,
             as_api=self.as_api,
@@ -144,8 +141,8 @@ def take_txn(*args, **kwargs):
         self.recoverer.recover()
         # shouldn't have called anything prior to waiting for exp backoff
         self.assertEquals(0, self.store.get_oldest_unsent_txn.call_count)
-        txn.send = Mock(return_value=make_awaitable(True))
-        txn.complete.return_value = make_awaitable(None)
+        txn.send = simple_async_mock(True)
+        txn.complete = simple_async_mock(None)
         # wait for exp backoff
         self.clock.advance_time(2)
         self.assertEquals(1, txn.send.call_count)
@@ -170,8 +167,8 @@ def take_txn(*args, **kwargs):
 
         self.recoverer.recover()
         self.assertEquals(0, self.store.get_oldest_unsent_txn.call_count)
-        txn.send = Mock(return_value=make_awaitable(False))
-        txn.complete.return_value = make_awaitable(None)
+        txn.send = simple_async_mock(False)
+        txn.complete = simple_async_mock(None)
         self.clock.advance_time(2)
         self.assertEquals(1, txn.send.call_count)
         self.assertEquals(0, txn.complete.call_count)
@@ -184,7 +181,7 @@ def take_txn(*args, **kwargs):
         self.assertEquals(3, txn.send.call_count)
         self.assertEquals(0, txn.complete.call_count)
         self.assertEquals(0, self.callback.call_count)
-        txn.send = Mock(return_value=make_awaitable(True))  # successfully send the txn
+        txn.send = simple_async_mock(True)  # successfully send the txn
         pop_txn = True  # returns the txn the first time, then no more.
         self.clock.advance_time(16)
         self.assertEquals(1, txn.send.call_count)  # new mock reset call count
@@ -195,6 +192,7 @@ def take_txn(*args, **kwargs):
 class ApplicationServiceSchedulerQueuerTestCase(unittest.TestCase):
     def setUp(self):
         self.txn_ctrl = Mock()
+        self.txn_ctrl.send = simple_async_mock()
         self.queuer = _ServiceQueuer(self.txn_ctrl, MockClock())
 
     def test_send_single_event_no_queue(self):
diff --git a/tests/config/test_base.py b/tests/config/test_base.py
index baa5313fb..6a52f862f 100644
--- a/tests/config/test_base.py
+++ b/tests/config/test_base.py
@@ -14,23 +14,28 @@
 
 import os.path
 import tempfile
+from unittest.mock import Mock
 
 from synapse.config import ConfigError
+from synapse.config._base import Config
 from synapse.util.stringutils import random_string
 
 from tests import unittest
 
 
-class BaseConfigTestCase(unittest.HomeserverTestCase):
-    def prepare(self, reactor, clock, hs):
-        self.hs = hs
+class BaseConfigTestCase(unittest.TestCase):
+    def setUp(self):
+        # The root object needs a server property with a public_baseurl.
+        root = Mock()
+        root.server.public_baseurl = "http://test"
+        self.config = Config(root)
 
     def test_loading_missing_templates(self):
         # Use a temporary directory that exists on the system, but that isn't likely to
         # contain template files
         with tempfile.TemporaryDirectory() as tmp_dir:
             # Attempt to load an HTML template from our custom template directory
-            template = self.hs.config.read_templates(["sso_error.html"], (tmp_dir,))[0]
+            template = self.config.read_templates(["sso_error.html"], (tmp_dir,))[0]
 
         # If no errors, we should've gotten the default template instead
 
@@ -60,7 +65,7 @@ def test_loading_custom_templates(self):
 
                 # Attempt to load the template from our custom template directory
                 template = (
-                    self.hs.config.read_templates([template_filename], (tmp_dir,))
+                    self.config.read_templates([template_filename], (tmp_dir,))
                 )[0]
 
         # Render the template
@@ -97,7 +102,7 @@ def test_multiple_custom_template_directories(self):
 
         # Retrieve the template.
         template = (
-            self.hs.config.read_templates(
+            self.config.read_templates(
                 [template_filename],
                 (td.name for td in tempdirs),
             )
@@ -118,7 +123,7 @@ def test_multiple_custom_template_directories(self):
 
         # Retrieve the template.
         template = (
-            self.hs.config.read_templates(
+            self.config.read_templates(
                 [other_template_name],
                 (td.name for td in tempdirs),
             )
@@ -134,6 +139,6 @@ def test_multiple_custom_template_directories(self):
 
     def test_loading_template_from_nonexistent_custom_directory(self):
         with self.assertRaises(ConfigError):
-            self.hs.config.read_templates(
+            self.config.read_templates(
                 ["some_filename.html"], ("a_nonexistent_directory",)
             )
diff --git a/tests/config/test_cache.py b/tests/config/test_cache.py
index 857d9cd09..4bb82e810 100644
--- a/tests/config/test_cache.py
+++ b/tests/config/test_cache.py
@@ -12,39 +12,34 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.config._base import Config, RootConfig
 from synapse.config.cache import CacheConfig, add_resizable_cache
 from synapse.util.caches.lrucache import LruCache
 
 from tests.unittest import TestCase
 
 
-class FakeServer(Config):
-    section = "server"
-
-
-class TestConfig(RootConfig):
-    config_classes = [FakeServer, CacheConfig]
-
-
 class CacheConfigTests(TestCase):
     def setUp(self):
-        # Reset caches before each test
-        TestConfig().caches.reset()
+        # Reset caches before each test since there's global state involved.
+        self.config = CacheConfig()
+        self.config.reset()
+
+    def tearDown(self):
+        # Also reset the caches after each test to leave state pristine.
+        self.config.reset()
 
     def test_individual_caches_from_environ(self):
         """
         Individual cache factors will be loaded from the environment.
         """
         config = {}
-        t = TestConfig()
-        t.caches._environ = {
+        self.config._environ = {
             "SYNAPSE_CACHE_FACTOR_SOMETHING_OR_OTHER": "2",
             "SYNAPSE_NOT_CACHE": "BLAH",
         }
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
-        self.assertEqual(dict(t.caches.cache_factors), {"something_or_other": 2.0})
+        self.assertEqual(dict(self.config.cache_factors), {"something_or_other": 2.0})
 
     def test_config_overrides_environ(self):
         """
@@ -52,15 +47,14 @@ def test_config_overrides_environ(self):
         over those in the config.
         """
         config = {"caches": {"per_cache_factors": {"foo": 2, "bar": 3}}}
-        t = TestConfig()
-        t.caches._environ = {
+        self.config._environ = {
             "SYNAPSE_CACHE_FACTOR_SOMETHING_OR_OTHER": "2",
             "SYNAPSE_CACHE_FACTOR_FOO": 1,
         }
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
         self.assertEqual(
-            dict(t.caches.cache_factors),
+            dict(self.config.cache_factors),
             {"foo": 1.0, "bar": 3.0, "something_or_other": 2.0},
         )
 
@@ -76,8 +70,7 @@ def test_individual_instantiated_before_config_load(self):
         self.assertEqual(cache.max_size, 50)
 
         config = {"caches": {"per_cache_factors": {"foo": 3}}}
-        t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config)
 
         self.assertEqual(cache.max_size, 300)
 
@@ -88,8 +81,7 @@ def test_individual_instantiated_after_config_load(self):
         there is one.
         """
         config = {"caches": {"per_cache_factors": {"foo": 2}}}
-        t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
         cache = LruCache(100)
         add_resizable_cache("foo", cache_resize_callback=cache.set_cache_factor)
@@ -106,8 +98,7 @@ def test_global_instantiated_before_config_load(self):
         self.assertEqual(cache.max_size, 50)
 
         config = {"caches": {"global_factor": 4}}
-        t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
         self.assertEqual(cache.max_size, 400)
 
@@ -118,8 +109,7 @@ def test_global_instantiated_after_config_load(self):
         is no per-cache factor.
         """
         config = {"caches": {"global_factor": 1.5}}
-        t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
         cache = LruCache(100)
         add_resizable_cache("foo", cache_resize_callback=cache.set_cache_factor)
@@ -133,12 +123,11 @@ def test_cache_with_asterisk_in_name(self):
                 "per_cache_factors": {"*cache_a*": 5, "cache_b": 6, "cache_c": 2}
             }
         }
-        t = TestConfig()
-        t.caches._environ = {
+        self.config._environ = {
             "SYNAPSE_CACHE_FACTOR_CACHE_A": "2",
             "SYNAPSE_CACHE_FACTOR_CACHE_B": 3,
         }
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
         cache_a = LruCache(100)
         add_resizable_cache("*cache_a*", cache_resize_callback=cache_a.set_cache_factor)
@@ -158,11 +147,10 @@ def test_apply_cache_factor_from_config(self):
         """
 
         config = {"caches": {"event_cache_size": "10k"}}
-        t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        self.config.read_config(config, config_dir_path="", data_dir_path="")
 
         cache = LruCache(
-            max_size=t.caches.event_cache_size,
+            max_size=self.config.event_cache_size,
             apply_cache_factor_from_config=False,
         )
         add_resizable_cache("event_cache", cache_resize_callback=cache.set_cache_factor)
diff --git a/tests/config/test_load.py b/tests/config/test_load.py
index ef6c2beec..59635de20 100644
--- a/tests/config/test_load.py
+++ b/tests/config/test_load.py
@@ -49,7 +49,7 @@ def test_generates_and_loads_macaroon_secret_key(self):
 
         config = HomeServerConfig.load_config("", ["-c", self.file])
         self.assertTrue(
-            hasattr(config, "macaroon_secret_key"),
+            hasattr(config.key, "macaroon_secret_key"),
             "Want config to have attr macaroon_secret_key",
         )
         if len(config.key.macaroon_secret_key) < 5:
@@ -60,7 +60,7 @@ def test_generates_and_loads_macaroon_secret_key(self):
 
         config = HomeServerConfig.load_or_generate_config("", ["-c", self.file])
         self.assertTrue(
-            hasattr(config, "macaroon_secret_key"),
+            hasattr(config.key, "macaroon_secret_key"),
             "Want config to have attr macaroon_secret_key",
         )
         if len(config.key.macaroon_secret_key) < 5:
@@ -74,8 +74,12 @@ def test_load_succeeds_if_macaroon_secret_key_missing(self):
         config1 = HomeServerConfig.load_config("", ["-c", self.file])
         config2 = HomeServerConfig.load_config("", ["-c", self.file])
         config3 = HomeServerConfig.load_or_generate_config("", ["-c", self.file])
-        self.assertEqual(config1.macaroon_secret_key, config2.macaroon_secret_key)
-        self.assertEqual(config1.macaroon_secret_key, config3.macaroon_secret_key)
+        self.assertEqual(
+            config1.key.macaroon_secret_key, config2.key.macaroon_secret_key
+        )
+        self.assertEqual(
+            config1.key.macaroon_secret_key, config3.key.macaroon_secret_key
+        )
 
     def test_disable_registration(self):
         self.generate_config()
@@ -84,16 +88,16 @@ def test_disable_registration(self):
         )
         # Check that disable_registration clobbers enable_registration.
         config = HomeServerConfig.load_config("", ["-c", self.file])
-        self.assertFalse(config.enable_registration)
+        self.assertFalse(config.registration.enable_registration)
 
         config = HomeServerConfig.load_or_generate_config("", ["-c", self.file])
-        self.assertFalse(config.enable_registration)
+        self.assertFalse(config.registration.enable_registration)
 
         # Check that either config value is clobbered by the command line.
         config = HomeServerConfig.load_or_generate_config(
             "", ["-c", self.file, "--enable-registration"]
         )
-        self.assertTrue(config.enable_registration)
+        self.assertTrue(config.registration.enable_registration)
 
     def test_stats_enabled(self):
         self.generate_config_and_remove_lines_containing("enable_metrics")
diff --git a/tests/config/test_tls.py b/tests/config/test_tls.py
index b6bc1876b..9ba578157 100644
--- a/tests/config/test_tls.py
+++ b/tests/config/test_tls.py
@@ -42,9 +42,9 @@ def test_tls_client_minimum_default(self):
         """
         config = {}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
 
-        self.assertEqual(t.federation_client_minimum_tls_version, "1")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1")
 
     def test_tls_client_minimum_set(self):
         """
@@ -52,29 +52,29 @@ def test_tls_client_minimum_set(self):
         """
         config = {"federation_client_minimum_tls_version": 1}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
-        self.assertEqual(t.federation_client_minimum_tls_version, "1")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1")
 
         config = {"federation_client_minimum_tls_version": 1.1}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
-        self.assertEqual(t.federation_client_minimum_tls_version, "1.1")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1.1")
 
         config = {"federation_client_minimum_tls_version": 1.2}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
-        self.assertEqual(t.federation_client_minimum_tls_version, "1.2")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1.2")
 
         # Also test a string version
         config = {"federation_client_minimum_tls_version": "1"}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
-        self.assertEqual(t.federation_client_minimum_tls_version, "1")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1")
 
         config = {"federation_client_minimum_tls_version": "1.2"}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
-        self.assertEqual(t.federation_client_minimum_tls_version, "1.2")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1.2")
 
     def test_tls_client_minimum_1_point_3_missing(self):
         """
@@ -91,7 +91,7 @@ def test_tls_client_minimum_1_point_3_missing(self):
         config = {"federation_client_minimum_tls_version": 1.3}
         t = TestConfig()
         with self.assertRaises(ConfigError) as e:
-            t.read_config(config, config_dir_path="", data_dir_path="")
+            t.tls.read_config(config, config_dir_path="", data_dir_path="")
         self.assertEqual(
             e.exception.args[0],
             (
@@ -112,8 +112,8 @@ def test_tls_client_minimum_1_point_3_exists(self):
 
         config = {"federation_client_minimum_tls_version": 1.3}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
-        self.assertEqual(t.federation_client_minimum_tls_version, "1.3")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
+        self.assertEqual(t.tls.federation_client_minimum_tls_version, "1.3")
 
     def test_tls_client_minimum_set_passed_through_1_2(self):
         """
@@ -121,7 +121,7 @@ def test_tls_client_minimum_set_passed_through_1_2(self):
         """
         config = {"federation_client_minimum_tls_version": 1.2}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
 
         cf = FederationPolicyForHTTPS(t)
         options = _get_ssl_context_options(cf._verify_ssl_context)
@@ -137,7 +137,7 @@ def test_tls_client_minimum_set_passed_through_1_0(self):
         """
         config = {"federation_client_minimum_tls_version": 1}
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
 
         cf = FederationPolicyForHTTPS(t)
         options = _get_ssl_context_options(cf._verify_ssl_context)
@@ -159,7 +159,7 @@ def test_whitelist_idna_failure(self):
         }
         t = TestConfig()
         e = self.assertRaises(
-            ConfigError, t.read_config, config, config_dir_path="", data_dir_path=""
+            ConfigError, t.tls.read_config, config, config_dir_path="", data_dir_path=""
         )
         self.assertIn("IDNA domain names", str(e))
 
@@ -174,7 +174,7 @@ def test_whitelist_idna_result(self):
             ]
         }
         t = TestConfig()
-        t.read_config(config, config_dir_path="", data_dir_path="")
+        t.tls.read_config(config, config_dir_path="", data_dir_path="")
 
         cf = FederationPolicyForHTTPS(t)
 
diff --git a/tests/events/test_presence_router.py b/tests/events/test_presence_router.py
index 3b3866bff..3deb14c30 100644
--- a/tests/events/test_presence_router.py
+++ b/tests/events/test_presence_router.py
@@ -26,6 +26,7 @@
 from synapse.types import JsonDict, StreamToken, create_requester
 
 from tests.handlers.test_sync import generate_sync_config
+from tests.test_utils import simple_async_mock
 from tests.unittest import FederatingHomeserverTestCase, TestCase, override_config
 
 
@@ -133,8 +134,12 @@ class PresenceRouterTestCase(FederatingHomeserverTestCase):
     ]
 
     def make_homeserver(self, reactor, clock):
+        # Mock out the calls over federation.
+        fed_transport_client = Mock(spec=["send_transaction"])
+        fed_transport_client.send_transaction = simple_async_mock({})
+
         hs = self.setup_test_homeserver(
-            federation_transport_client=Mock(spec=["send_transaction"]),
+            federation_transport_client=fed_transport_client,
         )
         # Load the modules into the homeserver
         module_api = hs.get_module_api()
diff --git a/tests/federation/test_federation_sender.py b/tests/federation/test_federation_sender.py
index 65b18fbd7..b457dad6d 100644
--- a/tests/federation/test_federation_sender.py
+++ b/tests/federation/test_federation_sender.py
@@ -336,7 +336,7 @@ def test_unreachable_server(self):
         recovery
         """
         mock_send_txn = self.hs.get_federation_transport_client().send_transaction
-        mock_send_txn.side_effect = lambda t, cb: defer.fail("fail")
+        mock_send_txn.side_effect = lambda t, cb: defer.fail(AssertionError("fail"))
 
         # create devices
         u1 = self.register_user("user", "pass")
@@ -376,7 +376,7 @@ def test_prune_outbound_device_pokes1(self):
         This case tests the behaviour when the server has never been reachable.
         """
         mock_send_txn = self.hs.get_federation_transport_client().send_transaction
-        mock_send_txn.side_effect = lambda t, cb: defer.fail("fail")
+        mock_send_txn.side_effect = lambda t, cb: defer.fail(AssertionError("fail"))
 
         # create devices
         u1 = self.register_user("user", "pass")
@@ -429,7 +429,7 @@ def test_prune_outbound_device_pokes2(self):
 
         # now the server goes offline
         mock_send_txn = self.hs.get_federation_transport_client().send_transaction
-        mock_send_txn.side_effect = lambda t, cb: defer.fail("fail")
+        mock_send_txn.side_effect = lambda t, cb: defer.fail(AssertionError("fail"))
 
         self.login("user", "pass", device_id="D2")
         self.login("user", "pass", device_id="D3")
diff --git a/tests/federation/test_federation_server.py b/tests/federation/test_federation_server.py
index 0b60cc426..03e1e11f4 100644
--- a/tests/federation/test_federation_server.py
+++ b/tests/federation/test_federation_server.py
@@ -120,7 +120,7 @@ def test_without_event_id(self):
 
         self.assertEqual(
             channel.json_body["room_version"],
-            self.hs.config.default_room_version.identifier,
+            self.hs.config.server.default_room_version.identifier,
         )
 
         members = set(
diff --git a/tests/handlers/test_profile.py b/tests/handlers/test_profile.py
index 54cb75673..42ff72a94 100644
--- a/tests/handlers/test_profile.py
+++ b/tests/handlers/test_profile.py
@@ -110,7 +110,7 @@ def test_set_my_name(self):
         )
 
     def test_set_my_name_if_disabled(self):
-        self.hs.config.enable_set_displayname = False
+        self.hs.config.registration.enable_set_displayname = False
 
         # Setting displayname for the first time is allowed
         self.get_success(
@@ -225,7 +225,7 @@ def test_set_my_avatar(self):
         )
 
     def test_set_my_avatar_if_disabled(self):
-        self.hs.config.enable_set_avatar_url = False
+        self.hs.config.registration.enable_set_avatar_url = False
 
         # Setting displayname for the first time is allowed
         self.get_success(
diff --git a/tests/handlers/test_register.py b/tests/handlers/test_register.py
index 6b993defd..f38e18ee2 100644
--- a/tests/handlers/test_register.py
+++ b/tests/handlers/test_register.py
@@ -16,7 +16,12 @@
 
 from synapse.api.auth import Auth
 from synapse.api.constants import UserTypes
-from synapse.api.errors import Codes, ResourceLimitError, SynapseError
+from synapse.api.errors import (
+    CodeMessageException,
+    Codes,
+    ResourceLimitError,
+    SynapseError,
+)
 from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.rest.client.register import _map_email_to_displayname, register_servlets
 from synapse.spam_checker_api import RegistrationBehaviour
@@ -126,14 +131,24 @@ def make_homeserver(self, reactor, clock):
         hs_config = self.default_config()
 
         # some of the tests rely on us having a user consent version
-        hs_config["user_consent"] = {
-            "version": "test_consent_version",
-            "template_dir": ".",
-        }
+        hs_config.setdefault("user_consent", {}).update(
+            {
+                "version": "test_consent_version",
+                "template_dir": ".",
+            }
+        )
         hs_config["max_mau_value"] = 50
         hs_config["limit_usage_by_mau"] = True
 
-        hs = self.setup_test_homeserver(config=hs_config)
+        # Don't attempt to reach out over federation.
+        self.mock_federation_client = Mock()
+        self.mock_federation_client.make_query.side_effect = CodeMessageException(
+            500, ""
+        )
+
+        hs = self.setup_test_homeserver(
+            config=hs_config, federation_client=self.mock_federation_client
+        )
 
         load_legacy_spam_checkers(hs)
 
@@ -144,9 +159,6 @@ def make_homeserver(self, reactor, clock):
         return hs
 
     def prepare(self, reactor, clock, hs):
-        self.mock_distributor = Mock()
-        self.mock_distributor.declare("registered_user")
-        self.mock_captcha_client = Mock()
         self.handler = self.hs.get_registration_handler()
         self.store = self.hs.get_datastore()
         self.lots_of_users = 100
@@ -180,21 +192,21 @@ def test_if_user_exists(self):
         self.assertEquals(result_user_id, user_id)
         self.assertTrue(result_token is not None)
 
+    @override_config({"limit_usage_by_mau": False})
     def test_mau_limits_when_disabled(self):
-        self.hs.config.limit_usage_by_mau = False
         # Ensure does not throw exception
         self.get_success(self.get_or_create_user(self.requester, "a", "display_name"))
 
+    @override_config({"limit_usage_by_mau": True})
     def test_get_or_create_user_mau_not_blocked(self):
-        self.hs.config.limit_usage_by_mau = True
         self.store.count_monthly_users = Mock(
-            return_value=make_awaitable(self.hs.config.max_mau_value - 1)
+            return_value=make_awaitable(self.hs.config.server.max_mau_value - 1)
         )
         # Ensure does not throw exception
         self.get_success(self.get_or_create_user(self.requester, "c", "User"))
 
+    @override_config({"limit_usage_by_mau": True})
     def test_get_or_create_user_mau_blocked(self):
-        self.hs.config.limit_usage_by_mau = True
         self.store.get_monthly_active_count = Mock(
             return_value=make_awaitable(self.lots_of_users)
         )
@@ -204,15 +216,15 @@ def test_get_or_create_user_mau_blocked(self):
         )
 
         self.store.get_monthly_active_count = Mock(
-            return_value=make_awaitable(self.hs.config.max_mau_value)
+            return_value=make_awaitable(self.hs.config.server.max_mau_value)
         )
         self.get_failure(
             self.get_or_create_user(self.requester, "b", "display_name"),
             ResourceLimitError,
         )
 
+    @override_config({"limit_usage_by_mau": True})
     def test_register_mau_blocked(self):
-        self.hs.config.limit_usage_by_mau = True
         self.store.get_monthly_active_count = Mock(
             return_value=make_awaitable(self.lots_of_users)
         )
@@ -221,16 +233,16 @@ def test_register_mau_blocked(self):
         )
 
         self.store.get_monthly_active_count = Mock(
-            return_value=make_awaitable(self.hs.config.max_mau_value)
+            return_value=make_awaitable(self.hs.config.server.max_mau_value)
         )
         self.get_failure(
             self.handler.register_user(localpart="local_part"), ResourceLimitError
         )
 
+    @override_config(
+        {"auto_join_rooms": ["#room:test"], "auto_join_rooms_for_guests": False}
+    )
     def test_auto_join_rooms_for_guests(self):
-        room_alias_str = "#room:test"
-        self.hs.config.auto_join_rooms = [room_alias_str]
-        self.hs.config.auto_join_rooms_for_guests = False
         user_id = self.get_success(
             self.handler.register_user(localpart="jeff", make_guest=True),
         )
@@ -249,34 +261,33 @@ def test_auto_create_auto_join_rooms(self):
         self.assertTrue(room_id["room_id"] in rooms)
         self.assertEqual(len(rooms), 1)
 
+    @override_config({"auto_join_rooms": []})
     def test_auto_create_auto_join_rooms_with_no_rooms(self):
-        self.hs.config.auto_join_rooms = []
         frank = UserID.from_string("@frank:test")
         user_id = self.get_success(self.handler.register_user(frank.localpart))
         self.assertEqual(user_id, frank.to_string())
         rooms = self.get_success(self.store.get_rooms_for_user(user_id))
         self.assertEqual(len(rooms), 0)
 
+    @override_config({"auto_join_rooms": ["#room:another"]})
     def test_auto_create_auto_join_where_room_is_another_domain(self):
-        self.hs.config.auto_join_rooms = ["#room:another"]
         frank = UserID.from_string("@frank:test")
         user_id = self.get_success(self.handler.register_user(frank.localpart))
         self.assertEqual(user_id, frank.to_string())
         rooms = self.get_success(self.store.get_rooms_for_user(user_id))
         self.assertEqual(len(rooms), 0)
 
+    @override_config(
+        {"auto_join_rooms": ["#room:test"], "autocreate_auto_join_rooms": False}
+    )
     def test_auto_create_auto_join_where_auto_create_is_false(self):
-        self.hs.config.autocreate_auto_join_rooms = False
-        room_alias_str = "#room:test"
-        self.hs.config.auto_join_rooms = [room_alias_str]
         user_id = self.get_success(self.handler.register_user(localpart="jeff"))
         rooms = self.get_success(self.store.get_rooms_for_user(user_id))
         self.assertEqual(len(rooms), 0)
 
+    @override_config({"auto_join_rooms": ["#room:test"]})
     def test_auto_create_auto_join_rooms_when_user_is_not_a_real_user(self):
         room_alias_str = "#room:test"
-        self.hs.config.auto_join_rooms = [room_alias_str]
-
         self.store.is_real_user = Mock(return_value=make_awaitable(False))
         user_id = self.get_success(self.handler.register_user(localpart="support"))
         rooms = self.get_success(self.store.get_rooms_for_user(user_id))
@@ -300,10 +311,8 @@ def test_auto_create_auto_join_rooms_when_user_is_the_first_real_user(self):
         self.assertTrue(room_id["room_id"] in rooms)
         self.assertEqual(len(rooms), 1)
 
+    @override_config({"auto_join_rooms": ["#room:test"]})
     def test_auto_create_auto_join_rooms_when_user_is_not_the_first_real_user(self):
-        room_alias_str = "#room:test"
-        self.hs.config.auto_join_rooms = [room_alias_str]
-
         self.store.count_real_users = Mock(return_value=make_awaitable(2))
         self.store.is_real_user = Mock(return_value=make_awaitable(True))
         user_id = self.get_success(self.handler.register_user(localpart="real"))
@@ -516,6 +525,17 @@ def test_auto_create_auto_join_room_preset_invalid_permissions(self):
         self.assertEqual(rooms, set())
         self.assertEqual(invited_rooms, [])
 
+    @override_config(
+        {
+            "user_consent": {
+                "block_events_error": "Error",
+                "require_at_registration": True,
+            },
+            "form_secret": "53cr3t",
+            "public_baseurl": "http://test",
+            "auto_join_rooms": ["#room:test"],
+        },
+    )
     def test_auto_create_auto_join_where_no_consent(self):
         """Test to ensure that the first user is not auto-joined to a room if
         they have not given general consent.
@@ -527,25 +547,20 @@ def test_auto_create_auto_join_where_no_consent(self):
         #    * The server is configured to auto-join to a room
         # (and autocreate if necessary)
 
-        event_creation_handler = self.hs.get_event_creation_handler()
-        # (Messing with the internals of event_creation_handler is fragile
-        # but can't see a better way to do this. One option could be to subclass
-        # the test with custom config.)
-        event_creation_handler._block_events_without_consent_error = "Error"
-        event_creation_handler._consent_uri_builder = Mock()
-        room_alias_str = "#room:test"
-        self.hs.config.auto_join_rooms = [room_alias_str]
-
         # When:-
-        #   * the user is registered and post consent actions are called
+        #   * the user is registered
         user_id = self.get_success(self.handler.register_user(localpart="jeff"))
-        self.get_success(self.handler.post_consent_actions(user_id))
 
         # Then:-
         #   * Ensure that they have not been joined to the room
         rooms = self.get_success(self.store.get_rooms_for_user(user_id))
         self.assertEqual(len(rooms), 0)
 
+        # The user provides consent; ensure they are now in the rooms.
+        self.get_success(self.handler.post_consent_actions(user_id))
+        rooms = self.get_success(self.store.get_rooms_for_user(user_id))
+        self.assertEqual(len(rooms), 1)
+
     def test_register_support_user(self):
         user_id = self.get_success(
             self.handler.register_user(localpart="user", user_type=UserTypes.SUPPORT)
diff --git a/tests/handlers/test_stats.py b/tests/handlers/test_stats.py
index aa0a5f76e..216e0aa8b 100644
--- a/tests/handlers/test_stats.py
+++ b/tests/handlers/test_stats.py
@@ -109,12 +109,7 @@ def _perform_background_initial_update(self):
         # Do the initial population of the stats via the background update
         self._add_background_updates()
 
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
     def test_initial_room(self):
         """
@@ -146,12 +141,7 @@ def test_initial_room(self):
         # Do the initial population of the user directory via the background update
         self._add_background_updates()
 
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         r = self.get_success(self.get_all_room_state())
 
@@ -574,12 +564,7 @@ def test_incomplete_stats(self):
             )
         )
 
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         r1stats_complete = self._get_current_stats("room", r1)
         u1stats_complete = self._get_current_stats("user", u1)
diff --git a/tests/handlers/test_user_directory.py b/tests/handlers/test_user_directory.py
index 2f801111d..e3acb7b68 100644
--- a/tests/handlers/test_user_directory.py
+++ b/tests/handlers/test_user_directory.py
@@ -11,47 +11,245 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from typing import List, Tuple
-from unittest.mock import Mock
+from typing import Tuple
+from unittest.mock import Mock, patch
 from urllib.parse import quote
 
 from twisted.internet import defer
+from twisted.test.proto_helpers import MemoryReactor
 
 import synapse.rest.admin
 from synapse.api.constants import UserTypes
 from synapse.api.room_versions import RoomVersion, RoomVersions
-from synapse.rest.client import account, account_validity, login, room, user_directory
+from synapse.appservice import ApplicationService
+from synapse.rest.client import (
+    account,
+    account_validity,
+    login,
+    register,
+    room,
+    user_directory,
+)
+from synapse.server import HomeServer
 from synapse.storage.roommember import ProfileInfo
 from synapse.types import create_requester
+from synapse.util import Clock
 
 from tests import unittest
+from tests.storage.test_user_directory import GetUserDirectoryTables
+from tests.test_utils.event_injection import inject_member_event
 from tests.unittest import override_config
 
 
 class UserDirectoryTestCase(unittest.HomeserverTestCase):
-    """
-    Tests the UserDirectoryHandler.
+    """Tests the UserDirectoryHandler.
+
+    We're broadly testing two kinds of things here.
+
+    1. Check that we correctly update the user directory in response
+       to events (e.g. join a room, leave a room, change name, make public)
+    2. Check that the search logic behaves as expected.
+
+    The background process that rebuilds the user directory is tested in
+    tests/storage/test_user_directory.py.
     """
 
     servlets = [
         login.register_servlets,
         synapse.rest.admin.register_servlets,
+        register.register_servlets,
         room.register_servlets,
     ]
 
-    def make_homeserver(self, reactor, clock):
-
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         config = self.default_config()
         config["update_user_directory"] = True
-        return self.setup_test_homeserver(config=config)
 
-    def prepare(self, reactor, clock, hs):
+        self.appservice = ApplicationService(
+            token="i_am_an_app_service",
+            hostname="test",
+            id="1234",
+            namespaces={"users": [{"regex": r"@as_user.*", "exclusive": True}]},
+            # Note: this user does not match the regex above, so that tests
+            # can distinguish the sender from the AS user.
+            sender="@as_main:test",
+        )
+
+        mock_load_appservices = Mock(return_value=[self.appservice])
+        with patch(
+            "synapse.storage.databases.main.appservice.load_appservices",
+            mock_load_appservices,
+        ):
+            hs = self.setup_test_homeserver(config=config)
+        return hs
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.store = hs.get_datastore()
         self.handler = hs.get_user_directory_handler()
         self.event_builder_factory = self.hs.get_event_builder_factory()
         self.event_creation_handler = self.hs.get_event_creation_handler()
+        self.user_dir_helper = GetUserDirectoryTables(self.store)
+
+    def test_normal_user_pair(self) -> None:
+        """Sanity check that the room-sharing tables are updated correctly."""
+        alice = self.register_user("alice", "pass")
+        alice_token = self.login(alice, "pass")
+        bob = self.register_user("bob", "pass")
+        bob_token = self.login(bob, "pass")
+
+        public = self.helper.create_room_as(
+            alice,
+            is_public=True,
+            extra_content={"visibility": "public"},
+            tok=alice_token,
+        )
+        private = self.helper.create_room_as(alice, is_public=False, tok=alice_token)
+        self.helper.invite(private, alice, bob, tok=alice_token)
+        self.helper.join(public, bob, tok=bob_token)
+        self.helper.join(private, bob, tok=bob_token)
+
+        # Alice also makes a second public room but no-one else joins
+        public2 = self.helper.create_room_as(
+            alice,
+            is_public=True,
+            extra_content={"visibility": "public"},
+            tok=alice_token,
+        )
+
+        users = self.get_success(self.user_dir_helper.get_users_in_user_directory())
+        in_public = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        in_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+
+        self.assertEqual(users, {alice, bob})
+        self.assertEqual(
+            set(in_public), {(alice, public), (bob, public), (alice, public2)}
+        )
+        self.assertEqual(
+            self.user_dir_helper._compress_shared(in_private),
+            {(alice, bob, private), (bob, alice, private)},
+        )
+
+    # The next four tests (test_excludes_*) all setup
+    #   - A normal user included in the user dir
+    #   - A public and private room created by that user
+    #   - A user excluded from the room dir, belonging to both rooms
+
+    # They match similar logic in storage/test_user_directory. But that tests
+    # rebuilding the directory; this tests updating it incrementally.
+
+    def test_excludes_support_user(self) -> None:
+        alice = self.register_user("alice", "pass")
+        alice_token = self.login(alice, "pass")
+        support = "@support1:test"
+        self.get_success(
+            self.store.register_user(
+                user_id=support, password_hash=None, user_type=UserTypes.SUPPORT
+            )
+        )
+
+        public, private = self._create_rooms_and_inject_memberships(
+            alice, alice_token, support
+        )
+        self._check_only_one_user_in_directory(alice, public)
+
+    def test_excludes_deactivated_user(self) -> None:
+        admin = self.register_user("admin", "pass", admin=True)
+        admin_token = self.login(admin, "pass")
+        user = self.register_user("naughty", "pass")
+
+        # Deactivate the user.
+        channel = self.make_request(
+            "PUT",
+            f"/_synapse/admin/v2/users/{user}",
+            access_token=admin_token,
+            content={"deactivated": True},
+        )
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(channel.json_body["deactivated"], True)
+
+        # Join the deactivated user to rooms owned by the admin.
+        # Is this something that could actually happen outside of a test?
+        public, private = self._create_rooms_and_inject_memberships(
+            admin, admin_token, user
+        )
+        self._check_only_one_user_in_directory(admin, public)
+
+    def test_excludes_appservices_user(self) -> None:
+        # Register an AS user.
+        user = self.register_user("user", "pass")
+        token = self.login(user, "pass")
+        as_user = self.register_appservice_user("as_user_potato", self.appservice.token)
+
+        # Join the AS user to rooms owned by the normal user.
+        public, private = self._create_rooms_and_inject_memberships(
+            user, token, as_user
+        )
+        self._check_only_one_user_in_directory(user, public)
+
+    def test_excludes_appservice_sender(self) -> None:
+        user = self.register_user("user", "pass")
+        token = self.login(user, "pass")
+        room = self.helper.create_room_as(user, is_public=True, tok=token)
+        self.helper.join(room, self.appservice.sender, tok=self.appservice.token)
+        self._check_only_one_user_in_directory(user, room)
+
+    def test_user_not_in_users_table(self) -> None:
+        """Unclear how it happens, but on matrix.org we've seen join events
+        for users who aren't in the users table. Test that we don't fall over
+        when processing such a user.
+        """
+        user1 = self.register_user("user1", "pass")
+        token1 = self.login(user1, "pass")
+        room = self.helper.create_room_as(user1, is_public=True, tok=token1)
+
+        # Inject a join event for a user who doesn't exist
+        self.get_success(inject_member_event(self.hs, room, "@not-a-user:test", "join"))
+
+        # Another new user registers and joins the room
+        user2 = self.register_user("user2", "pass")
+        token2 = self.login(user2, "pass")
+        self.helper.join(room, user2, tok=token2)
+
+        # The dodgy event should not have stopped us from processing user2's join.
+        in_public = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        self.assertEqual(set(in_public), {(user1, room), (user2, room)})
+
+    def _create_rooms_and_inject_memberships(
+        self, creator: str, token: str, joiner: str
+    ) -> Tuple[str, str]:
+        """Create a public and private room as a normal user.
+        Then get the `joiner` into those rooms.
+        """
+        # TODO: Duplicates the same-named method in UserDirectoryInitialPopulationTest.
+        public_room = self.helper.create_room_as(
+            creator,
+            is_public=True,
+            # See https://github.com/matrix-org/synapse/issues/10951
+            extra_content={"visibility": "public"},
+            tok=token,
+        )
+        private_room = self.helper.create_room_as(creator, is_public=False, tok=token)
 
-    def test_handle_local_profile_change_with_support_user(self):
+        # HACK: get the user into these rooms
+        self.get_success(inject_member_event(self.hs, public_room, joiner, "join"))
+        self.get_success(inject_member_event(self.hs, private_room, joiner, "join"))
+
+        return public_room, private_room
+
+    def _check_only_one_user_in_directory(self, user: str, public: str) -> None:
+        users = self.get_success(self.user_dir_helper.get_users_in_user_directory())
+        in_public = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        in_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+
+        self.assertEqual(users, {user})
+        self.assertEqual(set(in_public), {(user, public)})
+        self.assertEqual(in_private, [])
+
+    def test_handle_local_profile_change_with_support_user(self) -> None:
         support_user_id = "@support:test"
         self.get_success(
             self.store.register_user(
@@ -64,10 +262,12 @@ def test_handle_local_profile_change_with_support_user(self):
         )
 
         self.get_success(
-            self.handler.handle_local_profile_change(support_user_id, None)
+            self.handler.handle_local_profile_change(
+                support_user_id, ProfileInfo("I love support me", None)
+            )
         )
         profile = self.get_success(self.store.get_user_in_directory(support_user_id))
-        self.assertTrue(profile is None)
+        self.assertIsNone(profile)
         display_name = "display_name"
 
         profile_info = ProfileInfo(avatar_url="avatar_url", display_name=display_name)
@@ -77,7 +277,7 @@ def test_handle_local_profile_change_with_support_user(self):
         profile = self.get_success(self.store.get_user_in_directory(regular_user_id))
         self.assertTrue(profile["display_name"] == display_name)
 
-    def test_handle_local_profile_change_with_deactivated_user(self):
+    def test_handle_local_profile_change_with_deactivated_user(self) -> None:
         # create user
         r_user_id = "@regular:test"
         self.get_success(
@@ -101,7 +301,7 @@ def test_handle_local_profile_change_with_deactivated_user(self):
 
         # profile is not in directory
         profile = self.get_success(self.store.get_user_in_directory(r_user_id))
-        self.assertTrue(profile is None)
+        self.assertIsNone(profile)
 
         # update profile after deactivation
         self.get_success(
@@ -110,9 +310,50 @@ def test_handle_local_profile_change_with_deactivated_user(self):
 
         # profile is furthermore not in directory
         profile = self.get_success(self.store.get_user_in_directory(r_user_id))
-        self.assertTrue(profile is None)
+        self.assertIsNone(profile)
+
+    def test_handle_local_profile_change_with_appservice_user(self) -> None:
+        # create user
+        as_user_id = self.register_appservice_user(
+            "as_user_alice", self.appservice.token
+        )
+
+        # profile is not in directory
+        profile = self.get_success(self.store.get_user_in_directory(as_user_id))
+        self.assertIsNone(profile)
+
+        # update profile
+        profile_info = ProfileInfo(avatar_url="avatar_url", display_name="4L1c3")
+        self.get_success(
+            self.handler.handle_local_profile_change(as_user_id, profile_info)
+        )
+
+        # profile is still not in directory
+        profile = self.get_success(self.store.get_user_in_directory(as_user_id))
+        self.assertIsNone(profile)
+
+    def test_handle_local_profile_change_with_appservice_sender(self) -> None:
+        # profile is not in directory
+        profile = self.get_success(
+            self.store.get_user_in_directory(self.appservice.sender)
+        )
+        self.assertIsNone(profile)
+
+        # update profile
+        profile_info = ProfileInfo(avatar_url="avatar_url", display_name="4L1c3")
+        self.get_success(
+            self.handler.handle_local_profile_change(
+                self.appservice.sender, profile_info
+            )
+        )
+
+        # profile is still not in directory
+        profile = self.get_success(
+            self.store.get_user_in_directory(self.appservice.sender)
+        )
+        self.assertIsNone(profile)
 
-    def test_handle_user_deactivated_support_user(self):
+    def test_handle_user_deactivated_support_user(self) -> None:
         s_user_id = "@support:test"
         self.get_success(
             self.store.register_user(
@@ -120,20 +361,29 @@ def test_handle_user_deactivated_support_user(self):
             )
         )
 
-        self.store.remove_from_user_dir = Mock(return_value=defer.succeed(None))
-        self.get_success(self.handler.handle_local_user_deactivated(s_user_id))
-        self.store.remove_from_user_dir.not_called()
+        mock_remove_from_user_dir = Mock(return_value=defer.succeed(None))
+        with patch.object(
+            self.store, "remove_from_user_dir", mock_remove_from_user_dir
+        ):
+            self.get_success(self.handler.handle_local_user_deactivated(s_user_id))
+        # BUG: the correct spelling is assert_not_called, but that makes the test fail
+        # and it's not clear that this is actually the behaviour we want.
+        mock_remove_from_user_dir.not_called()
 
-    def test_handle_user_deactivated_regular_user(self):
+    def test_handle_user_deactivated_regular_user(self) -> None:
         r_user_id = "@regular:test"
         self.get_success(
             self.store.register_user(user_id=r_user_id, password_hash=None)
         )
-        self.store.remove_from_user_dir = Mock(return_value=defer.succeed(None))
-        self.get_success(self.handler.handle_local_user_deactivated(r_user_id))
-        self.store.remove_from_user_dir.called_once_with(r_user_id)
 
-    def test_reactivation_makes_regular_user_searchable(self):
+        mock_remove_from_user_dir = Mock(return_value=defer.succeed(None))
+        with patch.object(
+            self.store, "remove_from_user_dir", mock_remove_from_user_dir
+        ):
+            self.get_success(self.handler.handle_local_user_deactivated(r_user_id))
+        mock_remove_from_user_dir.assert_called_once_with(r_user_id)
+
+    def test_reactivation_makes_regular_user_searchable(self) -> None:
         user = self.register_user("regular", "pass")
         user_token = self.login(user, "pass")
         admin_user = self.register_user("admin", "pass", admin=True)
@@ -171,7 +421,147 @@ def test_reactivation_makes_regular_user_searchable(self):
         self.assertEqual(len(s["results"]), 1)
         self.assertEqual(s["results"][0]["user_id"], user)
 
-    def test_private_room(self):
+    def test_process_join_after_server_leaves_room(self) -> None:
+        alice = self.register_user("alice", "pass")
+        alice_token = self.login(alice, "pass")
+        bob = self.register_user("bob", "pass")
+        bob_token = self.login(bob, "pass")
+
+        # Alice makes two rooms. Bob joins one of them.
+        room1 = self.helper.create_room_as(alice, tok=alice_token)
+        room2 = self.helper.create_room_as(alice, tok=alice_token)
+        self.helper.join(room1, bob, tok=bob_token)
+
+        # The user sharing tables should have been updated.
+        public1 = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        self.assertEqual(set(public1), {(alice, room1), (alice, room2), (bob, room1)})
+
+        # Alice leaves room1. The user sharing tables should be updated.
+        self.helper.leave(room1, alice, tok=alice_token)
+        public2 = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        self.assertEqual(set(public2), {(alice, room2), (bob, room1)})
+
+        # Pause the processing of new events.
+        dir_handler = self.hs.get_user_directory_handler()
+        dir_handler.update_user_directory = False
+
+        # Bob leaves one room and joins the other.
+        self.helper.leave(room1, bob, tok=bob_token)
+        self.helper.join(room2, bob, tok=bob_token)
+
+        # Process the leave and join in one go.
+        dir_handler.update_user_directory = True
+        dir_handler.notify_new_event()
+        self.wait_for_background_updates()
+
+        # The user sharing tables should have been updated.
+        public3 = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        self.assertEqual(set(public3), {(alice, room2), (bob, room2)})
+
+    def test_per_room_profile_doesnt_alter_directory_entry(self) -> None:
+        alice = self.register_user("alice", "pass")
+        alice_token = self.login(alice, "pass")
+        bob = self.register_user("bob", "pass")
+
+        # Alice should have a user directory entry created at registration.
+        users = self.get_success(self.user_dir_helper.get_profiles_in_user_directory())
+        self.assertEqual(
+            users[alice], ProfileInfo(display_name="alice", avatar_url=None)
+        )
+
+        # Alice makes a room for herself.
+        room = self.helper.create_room_as(alice, is_public=True, tok=alice_token)
+
+        # Alice sets a nickname unique to that room.
+        self.helper.send_state(
+            room,
+            "m.room.member",
+            {
+                "displayname": "Freddy Mercury",
+                "membership": "join",
+            },
+            alice_token,
+            state_key=alice,
+        )
+
+        # Alice's display name remains the same in the user directory.
+        search_result = self.get_success(self.handler.search_users(bob, alice, 10))
+        self.assertEqual(
+            search_result["results"],
+            [{"display_name": "alice", "avatar_url": None, "user_id": alice}],
+            0,
+        )
+
+    def test_making_room_public_doesnt_alter_directory_entry(self) -> None:
+        """Per-room names shouldn't go to the directory when the room becomes public.
+
+        This isn't about preventing a leak (the room is now public, so the nickname
+        is too). It's about preserving the invariant that we only show a user's public
+        profile in the user directory results.
+
+        I made this a Synapse test case rather than a Complement one because
+        I think this is (strictly speaking) an implementation choice. Synapse
+        has chosen to only ever use the public profile when responding to a user
+        directory search. There's no privacy leak here, because making the room
+        public discloses the per-room name.
+
+        The spec doesn't mandate anything about _how_ a user
+        should appear in a /user_directory/search result. Hypothetical example:
+        suppose Bob searches for Alice. When representing Alice in a search
+        result, it's reasonable to use any of Alice's nicknames that Bob is
+        aware of. Heck, maybe we even want to use lots of them in a combined
+        displayname like `Alice (aka "ali", "ally", "41iC3")`.
+        """
+
+        # TODO the same should apply when Alice is a remote user.
+        alice = self.register_user("alice", "pass")
+        alice_token = self.login(alice, "pass")
+        bob = self.register_user("bob", "pass")
+        bob_token = self.login(bob, "pass")
+
+        # Alice and Bob are in a private room.
+        room = self.helper.create_room_as(alice, is_public=False, tok=alice_token)
+        self.helper.invite(room, src=alice, targ=bob, tok=alice_token)
+        self.helper.join(room, user=bob, tok=bob_token)
+
+        # Alice has a nickname unique to that room.
+
+        self.helper.send_state(
+            room,
+            "m.room.member",
+            {
+                "displayname": "Freddy Mercury",
+                "membership": "join",
+            },
+            alice_token,
+            state_key=alice,
+        )
+
+        # Check Alice isn't recorded as being in a public room.
+        public = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        self.assertNotIn((alice, room), public)
+
+        # One of them makes the room public.
+        self.helper.send_state(
+            room,
+            "m.room.join_rules",
+            {"join_rule": "public"},
+            alice_token,
+        )
+
+        # Check that Alice is now recorded as being in a public room
+        public = self.get_success(self.user_dir_helper.get_users_in_public_rooms())
+        self.assertIn((alice, room), public)
+
+        # Alice's display name remains the same in the user directory.
+        search_result = self.get_success(self.handler.search_users(bob, alice, 10))
+        self.assertEqual(
+            search_result["results"],
+            [{"display_name": "alice", "avatar_url": None, "user_id": alice}],
+            0,
+        )
+
+    def test_private_room(self) -> None:
         """
         A user can be searched for only by people that are either in a public
         room, or that share a private chat.
@@ -191,11 +581,16 @@ def test_private_room(self):
         self.helper.join(room, user=u2, tok=u2_token)
 
         # Check we have populated the database correctly.
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
 
         self.assertEqual(
-            self._compress_shared(shares_private), {(u1, u2, room), (u2, u1, room)}
+            self.user_dir_helper._compress_shared(shares_private),
+            {(u1, u2, room), (u2, u1, room)},
         )
         self.assertEqual(public_users, [])
 
@@ -215,10 +610,14 @@ def test_private_room(self):
         self.helper.leave(room, user=u2, tok=u2_token)
 
         # Check we have removed the values.
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
 
-        self.assertEqual(self._compress_shared(shares_private), set())
+        self.assertEqual(self.user_dir_helper._compress_shared(shares_private), set())
         self.assertEqual(public_users, [])
 
         # User1 now gets no search results for any of the other users.
@@ -228,7 +627,7 @@ def test_private_room(self):
         s = self.get_success(self.handler.search_users(u1, "user3", 10))
         self.assertEqual(len(s["results"]), 0)
 
-    def test_spam_checker(self):
+    def test_spam_checker(self) -> None:
         """
         A user which fails the spam checks will not appear in search results.
         """
@@ -246,11 +645,16 @@ def test_spam_checker(self):
         self.helper.join(room, user=u2, tok=u2_token)
 
         # Check we have populated the database correctly.
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
 
         self.assertEqual(
-            self._compress_shared(shares_private), {(u1, u2, room), (u2, u1, room)}
+            self.user_dir_helper._compress_shared(shares_private),
+            {(u1, u2, room), (u2, u1, room)},
         )
         self.assertEqual(public_users, [])
 
@@ -258,7 +662,7 @@ def test_spam_checker(self):
         s = self.get_success(self.handler.search_users(u1, "user2", 10))
         self.assertEqual(len(s["results"]), 1)
 
-        async def allow_all(user_profile):
+        async def allow_all(user_profile: ProfileInfo) -> bool:
             # Allow all users.
             return False
 
@@ -272,7 +676,7 @@ async def allow_all(user_profile):
         self.assertEqual(len(s["results"]), 1)
 
         # Configure a spam checker that filters all users.
-        async def block_all(user_profile):
+        async def block_all(user_profile: ProfileInfo) -> bool:
             # All users are spammy.
             return True
 
@@ -282,7 +686,7 @@ async def block_all(user_profile):
         s = self.get_success(self.handler.search_users(u1, "user2", 10))
         self.assertEqual(len(s["results"]), 0)
 
-    def test_legacy_spam_checker(self):
+    def test_legacy_spam_checker(self) -> None:
         """
         A spam checker without the expected method should be ignored.
         """
@@ -300,11 +704,16 @@ def test_legacy_spam_checker(self):
         self.helper.join(room, user=u2, tok=u2_token)
 
         # Check we have populated the database correctly.
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
 
         self.assertEqual(
-            self._compress_shared(shares_private), {(u1, u2, room), (u2, u1, room)}
+            self.user_dir_helper._compress_shared(shares_private),
+            {(u1, u2, room), (u2, u1, room)},
         )
         self.assertEqual(public_users, [])
 
@@ -317,134 +726,7 @@ def test_legacy_spam_checker(self):
         s = self.get_success(self.handler.search_users(u1, "user2", 10))
         self.assertEqual(len(s["results"]), 1)
 
-    def _compress_shared(self, shared):
-        """
-        Compress a list of users who share rooms dicts to a list of tuples.
-        """
-        r = set()
-        for i in shared:
-            r.add((i["user_id"], i["other_user_id"], i["room_id"]))
-        return r
-
-    def get_users_in_public_rooms(self) -> List[Tuple[str, str]]:
-        r = self.get_success(
-            self.store.db_pool.simple_select_list(
-                "users_in_public_rooms", None, ("user_id", "room_id")
-            )
-        )
-        retval = []
-        for i in r:
-            retval.append((i["user_id"], i["room_id"]))
-        return retval
-
-    def get_users_who_share_private_rooms(self) -> List[Tuple[str, str, str]]:
-        return self.get_success(
-            self.store.db_pool.simple_select_list(
-                "users_who_share_private_rooms",
-                None,
-                ["user_id", "other_user_id", "room_id"],
-            )
-        )
-
-    def _add_background_updates(self):
-        """
-        Add the background updates we need to run.
-        """
-        # Ugh, have to reset this flag
-        self.store.db_pool.updates._all_done = False
-
-        self.get_success(
-            self.store.db_pool.simple_insert(
-                "background_updates",
-                {
-                    "update_name": "populate_user_directory_createtables",
-                    "progress_json": "{}",
-                },
-            )
-        )
-        self.get_success(
-            self.store.db_pool.simple_insert(
-                "background_updates",
-                {
-                    "update_name": "populate_user_directory_process_rooms",
-                    "progress_json": "{}",
-                    "depends_on": "populate_user_directory_createtables",
-                },
-            )
-        )
-        self.get_success(
-            self.store.db_pool.simple_insert(
-                "background_updates",
-                {
-                    "update_name": "populate_user_directory_process_users",
-                    "progress_json": "{}",
-                    "depends_on": "populate_user_directory_process_rooms",
-                },
-            )
-        )
-        self.get_success(
-            self.store.db_pool.simple_insert(
-                "background_updates",
-                {
-                    "update_name": "populate_user_directory_cleanup",
-                    "progress_json": "{}",
-                    "depends_on": "populate_user_directory_process_users",
-                },
-            )
-        )
-
-    def test_initial(self):
-        """
-        The user directory's initial handler correctly updates the search tables.
-        """
-        u1 = self.register_user("user1", "pass")
-        u1_token = self.login(u1, "pass")
-        u2 = self.register_user("user2", "pass")
-        u2_token = self.login(u2, "pass")
-        u3 = self.register_user("user3", "pass")
-        u3_token = self.login(u3, "pass")
-
-        room = self.helper.create_room_as(u1, is_public=True, tok=u1_token)
-        self.helper.invite(room, src=u1, targ=u2, tok=u1_token)
-        self.helper.join(room, user=u2, tok=u2_token)
-
-        private_room = self.helper.create_room_as(u1, is_public=False, tok=u1_token)
-        self.helper.invite(private_room, src=u1, targ=u3, tok=u1_token)
-        self.helper.join(private_room, user=u3, tok=u3_token)
-
-        self.get_success(self.store.update_user_directory_stream_pos(None))
-        self.get_success(self.store.delete_all_from_user_dir())
-
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
-
-        # Nothing updated yet
-        self.assertEqual(shares_private, [])
-        self.assertEqual(public_users, [])
-
-        # Do the initial population of the user directory via the background update
-        self._add_background_updates()
-
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
-
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
-
-        # User 1 and User 2 are in the same public room
-        self.assertEqual(set(public_users), {(u1, room), (u2, room)})
-
-        # User 1 and User 3 share private rooms
-        self.assertEqual(
-            self._compress_shared(shares_private),
-            {(u1, u3, private_room), (u3, u1, private_room)},
-        )
-
-    def test_initial_share_all_users(self):
+    def test_initial_share_all_users(self) -> None:
         """
         Search all users = True means that a user does not have to share a
         private room with the searching user or be in a public room to be search
@@ -457,26 +739,16 @@ def test_initial_share_all_users(self):
         self.register_user("user2", "pass")
         u3 = self.register_user("user3", "pass")
 
-        # Wipe the user dir
-        self.get_success(self.store.update_user_directory_stream_pos(None))
-        self.get_success(self.store.delete_all_from_user_dir())
-
-        # Do the initial population of the user directory via the background update
-        self._add_background_updates()
-
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
-
-        shares_private = self.get_users_who_share_private_rooms()
-        public_users = self.get_users_in_public_rooms()
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
 
         # No users share rooms
         self.assertEqual(public_users, [])
-        self.assertEqual(self._compress_shared(shares_private), set())
+        self.assertEqual(self.user_dir_helper._compress_shared(shares_private), set())
 
         # Despite not sharing a room, search_all_users means we get a search
         # result.
@@ -501,7 +773,7 @@ def test_initial_share_all_users(self):
             }
         }
     )
-    def test_prefer_local_users(self):
+    def test_prefer_local_users(self) -> None:
         """Tests that local users are shown higher in search results when
         user_directory.prefer_local_users is True.
         """
@@ -535,15 +807,6 @@ def test_prefer_local_users(self):
         local_users = [local_user_1, local_user_2, local_user_3]
         remote_users = [remote_user_1, remote_user_2, remote_user_3]
 
-        # Populate the user directory via background update
-        self._add_background_updates()
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
-
         # The local searching user searches for the term "user", which other users have
         # in their user id
         results = self.get_success(
@@ -565,7 +828,7 @@ def _add_user_to_room(
         room_id: str,
         room_version: RoomVersion,
         user_id: str,
-    ):
+    ) -> None:
         # Add a user to the room.
         builder = self.event_builder_factory.for_room_version(
             room_version,
@@ -588,8 +851,6 @@ def _add_user_to_room(
 
 
 class TestUserDirSearchDisabled(unittest.HomeserverTestCase):
-    user_id = "@test:test"
-
     servlets = [
         user_directory.register_servlets,
         room.register_servlets,
@@ -597,7 +858,7 @@ class TestUserDirSearchDisabled(unittest.HomeserverTestCase):
         synapse.rest.admin.register_servlets_for_client_rest_resource,
     ]
 
-    def make_homeserver(self, reactor, clock):
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         config = self.default_config()
         config["update_user_directory"] = True
         hs = self.setup_test_homeserver(config=config)
@@ -606,19 +867,24 @@ def make_homeserver(self, reactor, clock):
 
         return hs
 
-    def test_disabling_room_list(self):
+    def test_disabling_room_list(self) -> None:
         self.config.userdirectory.user_directory_search_enabled = True
 
-        # First we create a room with another user so that user dir is non-empty
-        # for our user
-        self.helper.create_room_as(self.user_id)
+        # Create two users and put them in the same room.
+        u1 = self.register_user("user1", "pass")
+        u1_token = self.login(u1, "pass")
         u2 = self.register_user("user2", "pass")
-        room = self.helper.create_room_as(self.user_id)
-        self.helper.join(room, user=u2)
+        u2_token = self.login(u2, "pass")
+
+        room = self.helper.create_room_as(u1, tok=u1_token)
+        self.helper.join(room, user=u2, tok=u2_token)
 
-        # Assert user directory is not empty
+        # Each should see the other when searching the user directory.
         channel = self.make_request(
-            "POST", b"user_directory/search", b'{"search_term":"user2"}'
+            "POST",
+            b"user_directory/search",
+            b'{"search_term":"user2"}',
+            access_token=u1_token,
         )
         self.assertEquals(200, channel.code, channel.result)
         self.assertTrue(len(channel.json_body["results"]) > 0)
@@ -626,7 +892,10 @@ def test_disabling_room_list(self):
         # Disable user directory and check search returns nothing
         self.config.userdirectory.user_directory_search_enabled = False
         channel = self.make_request(
-            "POST", b"user_directory/search", b'{"search_term":"user2"}'
+            "POST",
+            b"user_directory/search",
+            b'{"search_term":"user2"}',
+            access_token=u1_token,
         )
         self.assertEquals(200, channel.code, channel.result)
         self.assertTrue(len(channel.json_body["results"]) == 0)
diff --git a/tests/http/test_fedclient.py b/tests/http/test_fedclient.py
index d9a8b077d..638babae6 100644
--- a/tests/http/test_fedclient.py
+++ b/tests/http/test_fedclient.py
@@ -226,7 +226,7 @@ def test_client_ip_range_blacklist(self):
         """Ensure that Synapse does not try to connect to blacklisted IPs"""
 
         # Set up the ip_range blacklist
-        self.hs.config.federation_ip_range_blacklist = IPSet(
+        self.hs.config.server.federation_ip_range_blacklist = IPSet(
             ["127.0.0.0/8", "fe80::/64"]
         )
         self.reactor.lookups["internal"] = "127.0.0.1"
diff --git a/tests/logging/test_terse_json.py b/tests/logging/test_terse_json.py
index f73fcd684..96f399b7a 100644
--- a/tests/logging/test_terse_json.py
+++ b/tests/logging/test_terse_json.py
@@ -198,3 +198,31 @@ def test_with_request_context(self):
         self.assertEqual(log["url"], "/_matrix/client/versions")
         self.assertEqual(log["protocol"], "1.1")
         self.assertEqual(log["user_agent"], "")
+
+    def test_with_exception(self):
+        """
+        The logging exception type & value should be added to the JSON response.
+        """
+        handler = logging.StreamHandler(self.output)
+        handler.setFormatter(JsonFormatter())
+        logger = self.get_logger(handler)
+
+        try:
+            raise ValueError("That's wrong, you wally!")
+        except ValueError:
+            logger.exception("Hello there, %s!", "wally")
+
+        log = self.get_log_line()
+
+        # The terse logger should give us these keys.
+        expected_log_keys = [
+            "log",
+            "level",
+            "namespace",
+            "exc_type",
+            "exc_value",
+        ]
+        self.assertCountEqual(log.keys(), expected_log_keys)
+        self.assertEqual(log["log"], "Hello there, wally!")
+        self.assertEqual(log["exc_type"], "ValueError")
+        self.assertEqual(log["exc_value"], "That's wrong, you wally!")
diff --git a/tests/module_api/test_api.py b/tests/module_api/test_api.py
index 88a3659a9..5256633ef 100644
--- a/tests/module_api/test_api.py
+++ b/tests/module_api/test_api.py
@@ -25,6 +25,7 @@
 
 from tests.events.test_presence_router import send_presence_update, sync_presence
 from tests.replication._base import BaseMultiWorkerStreamTestCase
+from tests.test_utils import simple_async_mock
 from tests.test_utils.event_injection import inject_member_event
 from tests.unittest import HomeserverTestCase, override_config
 from tests.utils import USE_POSTGRES_FOR_TESTS
@@ -46,8 +47,12 @@ def prepare(self, reactor, clock, homeserver):
         self.auth_handler = homeserver.get_auth_handler()
 
     def make_homeserver(self, reactor, clock):
+        # Mock out the calls over federation.
+        fed_transport_client = Mock(spec=["send_transaction"])
+        fed_transport_client.send_transaction = simple_async_mock({})
+
         return self.setup_test_homeserver(
-            federation_transport_client=Mock(spec=["send_transaction"]),
+            federation_transport_client=fed_transport_client,
         )
 
     def test_can_register_user(self):
diff --git a/tests/replication/_base.py b/tests/replication/_base.py
index c7555c26d..eac4664b4 100644
--- a/tests/replication/_base.py
+++ b/tests/replication/_base.py
@@ -70,8 +70,16 @@ def prepare(self, reactor, clock, hs):
         # databases objects are the same.
         self.worker_hs.get_datastore().db_pool = hs.get_datastore().db_pool
 
+        # Normally we'd pass in the handler to `setup_test_homeserver`, which would
+        # eventually hit "Install @cache_in_self attributes" in tests/utils.py.
+        # Unfortunately our handler wants a reference to the homeserver. That leaves
+        # us with a chicken-and-egg problem.
+        # We can workaround this: create the homeserver first, create the handler
+        # and bodge it in after the fact. The bodging requires us to know the
+        # dirty details of how `cache_in_self` works. We politely ask mypy to
+        # ignore our dirty dealings.
         self.test_handler = self._build_replication_data_handler()
-        self.worker_hs._replication_data_handler = self.test_handler
+        self.worker_hs._replication_data_handler = self.test_handler  # type: ignore[attr-defined]
 
         repl_handler = ReplicationCommandHandler(self.worker_hs)
         self.client = ClientReplicationStreamProtocol(
@@ -240,7 +248,7 @@ def setUp(self):
         if self.hs.config.redis.redis_enabled:
             # Handle attempts to connect to fake redis server.
             self.reactor.add_tcp_client_callback(
-                b"localhost",
+                "localhost",
                 6379,
                 self.connect_any_redis_attempts,
             )
@@ -315,12 +323,15 @@ def make_worker_hs(
                     )
                 )
 
+            # Copy the port into a new, non-Optional variable so mypy knows we're
+            # not going to reset `instance_loc` to `None` under its feet. See
+            # https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
+            port = instance_loc.port
+
             self.reactor.add_tcp_client_callback(
                 self.reactor.lookups[instance_loc.host],
                 instance_loc.port,
-                lambda: self._handle_http_replication_attempt(
-                    worker_hs, instance_loc.port
-                ),
+                lambda: self._handle_http_replication_attempt(worker_hs, port),
             )
 
         store = worker_hs.get_datastore()
@@ -424,7 +435,7 @@ def connect_any_redis_attempts(self):
         clients = self.reactor.tcpClients
         while clients:
             (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
-            self.assertEqual(host, b"localhost")
+            self.assertEqual(host, "localhost")
             self.assertEqual(port, 6379)
 
             client_protocol = client_factory.buildProtocol(None)
diff --git a/tests/rest/admin/test_user.py b/tests/rest/admin/test_user.py
index b15fc0a74..2fd87be54 100644
--- a/tests/rest/admin/test_user.py
+++ b/tests/rest/admin/test_user.py
@@ -59,7 +59,7 @@ def make_homeserver(self, reactor, clock):
 
         self.hs = self.setup_test_homeserver()
 
-        self.hs.config.registration_shared_secret = "shared"
+        self.hs.config.registration.registration_shared_secret = "shared"
 
         self.hs.get_media_repository = Mock()
         self.hs.get_deactivate_account_handler = Mock()
@@ -71,7 +71,7 @@ def test_disabled(self):
         If there is no shared secret, registration through this method will be
         prevented.
         """
-        self.hs.config.registration_shared_secret = None
+        self.hs.config.registration.registration_shared_secret = None
 
         channel = self.make_request("POST", self.url, b"{}")
 
@@ -422,7 +422,7 @@ def test_register_mau_limit_reached(self):
 
         # Set monthly active users to the limit
         store.get_monthly_active_count = Mock(
-            return_value=make_awaitable(self.hs.config.max_mau_value)
+            return_value=make_awaitable(self.hs.config.server.max_mau_value)
         )
         # Check that the blocking of monthly active users is working as expected
         # The registration of a new user fails due to the limit
@@ -1490,7 +1490,7 @@ def test_create_user_mau_limit_reached_active_admin(self):
 
         # Set monthly active users to the limit
         self.store.get_monthly_active_count = Mock(
-            return_value=make_awaitable(self.hs.config.max_mau_value)
+            return_value=make_awaitable(self.hs.config.server.max_mau_value)
         )
         # Check that the blocking of monthly active users is working as expected
         # The registration of a new user fails due to the limit
@@ -1527,7 +1527,7 @@ def test_create_user_mau_limit_reached_passive_admin(self):
 
         # Set monthly active users to the limit
         self.store.get_monthly_active_count = Mock(
-            return_value=make_awaitable(self.hs.config.max_mau_value)
+            return_value=make_awaitable(self.hs.config.server.max_mau_value)
         )
         # Check that the blocking of monthly active users is working as expected
         # The registration of a new user fails due to the limit
diff --git a/tests/rest/client/test_account.py b/tests/rest/client/test_account.py
index 9e9e953cf..89d85b0a1 100644
--- a/tests/rest/client/test_account.py
+++ b/tests/rest/client/test_account.py
@@ -470,13 +470,45 @@ class WhoamiTestCase(unittest.HomeserverTestCase):
         register.register_servlets,
     ]
 
+    def default_config(self):
+        config = super().default_config()
+        config["allow_guest_access"] = True
+        return config
+
     def test_GET_whoami(self):
         device_id = "wouldgohere"
         user_id = self.register_user("kermit", "test")
         tok = self.login("kermit", "test", device_id=device_id)
 
-        whoami = self.whoami(tok)
-        self.assertEqual(whoami, {"user_id": user_id, "device_id": device_id})
+        whoami = self._whoami(tok)
+        self.assertEqual(
+            whoami,
+            {
+                "user_id": user_id,
+                "device_id": device_id,
+                # Unstable until MSC3069 enters spec
+                "org.matrix.msc3069.is_guest": False,
+            },
+        )
+
+    def test_GET_whoami_guests(self):
+        channel = self.make_request(
+            b"POST", b"/_matrix/client/r0/register?kind=guest", b"{}"
+        )
+        tok = channel.json_body["access_token"]
+        user_id = channel.json_body["user_id"]
+        device_id = channel.json_body["device_id"]
+
+        whoami = self._whoami(tok)
+        self.assertEqual(
+            whoami,
+            {
+                "user_id": user_id,
+                "device_id": device_id,
+                # Unstable until MSC3069 enters spec
+                "org.matrix.msc3069.is_guest": True,
+            },
+        )
 
     def test_GET_whoami_appservices(self):
         user_id = "@as:test"
@@ -484,18 +516,25 @@ def test_GET_whoami_appservices(self):
 
         appservice = ApplicationService(
             as_token,
-            self.hs.config.server_name,
+            self.hs.config.server.server_name,
             id="1234",
             namespaces={"users": [{"regex": user_id, "exclusive": True}]},
             sender=user_id,
         )
         self.hs.get_datastore().services_cache.append(appservice)
 
-        whoami = self.whoami(as_token)
-        self.assertEqual(whoami, {"user_id": user_id})
+        whoami = self._whoami(as_token)
+        self.assertEqual(
+            whoami,
+            {
+                "user_id": user_id,
+                # Unstable until MSC3069 enters spec
+                "org.matrix.msc3069.is_guest": False,
+            },
+        )
         self.assertFalse(hasattr(whoami, "device_id"))
 
-    def whoami(self, tok):
+    def _whoami(self, tok):
         channel = self.make_request("GET", "account/whoami", {}, access_token=tok)
         self.assertEqual(channel.code, 200)
         return channel.json_body
@@ -625,7 +664,7 @@ def test_ratelimit_by_ip(self):
 
     def test_add_email_if_disabled(self):
         """Test adding email to profile when doing so is disallowed"""
-        self.hs.config.enable_3pid_changes = False
+        self.hs.config.registration.enable_3pid_changes = False
 
         client_secret = "foobar"
         session_id = self._request_token(self.email, client_secret)
@@ -695,7 +734,7 @@ def test_delete_email(self):
 
     def test_delete_email_if_disabled(self):
         """Test deleting an email from profile when disallowed"""
-        self.hs.config.enable_3pid_changes = False
+        self.hs.config.registration.enable_3pid_changes = False
 
         # Add a threepid
         self.get_success(
diff --git a/tests/rest/client/test_capabilities.py b/tests/rest/client/test_capabilities.py
index 422361b62..b9e360255 100644
--- a/tests/rest/client/test_capabilities.py
+++ b/tests/rest/client/test_capabilities.py
@@ -55,7 +55,7 @@ def test_get_room_version_capabilities(self):
             self.assertTrue(room_version in KNOWN_ROOM_VERSIONS, "" + room_version)
 
         self.assertEqual(
-            self.config.default_room_version.identifier,
+            self.config.server.default_room_version.identifier,
             capabilities["m.room_versions"]["default"],
         )
 
diff --git a/tests/rest/client/test_identity.py b/tests/rest/client/test_identity.py
index 013b2049e..e0735ef4a 100644
--- a/tests/rest/client/test_identity.py
+++ b/tests/rest/client/test_identity.py
@@ -60,6 +60,8 @@ def test_3pid_invite_disabled(self):
         self.assertEquals(channel.result["code"], b"403", channel.result)
 
     def test_3pid_lookup_disabled(self):
+        self.hs.config.registration.enable_3pid_lookup = False
+
         url = (
             "/_matrix/client/unstable/account/3pid/lookup"
             "?id_server=testis&medium=email&address=foo@bar.baz"
diff --git a/tests/rest/client/test_login.py b/tests/rest/client/test_login.py
index 371615a01..a63f04bd4 100644
--- a/tests/rest/client/test_login.py
+++ b/tests/rest/client/test_login.py
@@ -94,9 +94,9 @@ class LoginRestServletTestCase(unittest.HomeserverTestCase):
 
     def make_homeserver(self, reactor, clock):
         self.hs = self.setup_test_homeserver()
-        self.hs.config.enable_registration = True
-        self.hs.config.registrations_require_3pid = []
-        self.hs.config.auto_join_rooms = []
+        self.hs.config.registration.enable_registration = True
+        self.hs.config.registration.registrations_require_3pid = []
+        self.hs.config.registration.auto_join_rooms = []
         self.hs.config.captcha.enable_registration_captcha = False
 
         return self.hs
@@ -1064,13 +1064,6 @@ class AppserviceLoginRestServletTestCase(unittest.HomeserverTestCase):
         register.register_servlets,
     ]
 
-    def register_as_user(self, username):
-        self.make_request(
-            b"POST",
-            "/_matrix/client/r0/register?access_token=%s" % (self.service.token,),
-            {"username": username},
-        )
-
     def make_homeserver(self, reactor, clock):
         self.hs = self.setup_test_homeserver()
 
@@ -1107,7 +1100,7 @@ def make_homeserver(self, reactor, clock):
 
     def test_login_appservice_user(self):
         """Test that an appservice user can use /login"""
-        self.register_as_user(AS_USER)
+        self.register_appservice_user(AS_USER, self.service.token)
 
         params = {
             "type": login.LoginRestServlet.APPSERVICE_TYPE,
@@ -1121,7 +1114,7 @@ def test_login_appservice_user(self):
 
     def test_login_appservice_user_bot(self):
         """Test that the appservice bot can use /login"""
-        self.register_as_user(AS_USER)
+        self.register_appservice_user(AS_USER, self.service.token)
 
         params = {
             "type": login.LoginRestServlet.APPSERVICE_TYPE,
@@ -1135,7 +1128,7 @@ def test_login_appservice_user_bot(self):
 
     def test_login_appservice_wrong_user(self):
         """Test that non-as users cannot login with the as token"""
-        self.register_as_user(AS_USER)
+        self.register_appservice_user(AS_USER, self.service.token)
 
         params = {
             "type": login.LoginRestServlet.APPSERVICE_TYPE,
@@ -1149,7 +1142,7 @@ def test_login_appservice_wrong_user(self):
 
     def test_login_appservice_wrong_as(self):
         """Test that as users cannot login with wrong as token"""
-        self.register_as_user(AS_USER)
+        self.register_appservice_user(AS_USER, self.service.token)
 
         params = {
             "type": login.LoginRestServlet.APPSERVICE_TYPE,
@@ -1165,7 +1158,7 @@ def test_login_appservice_no_token(self):
         """Test that users must provide a token when using the appservice
         login method
         """
-        self.register_as_user(AS_USER)
+        self.register_appservice_user(AS_USER, self.service.token)
 
         params = {
             "type": login.LoginRestServlet.APPSERVICE_TYPE,
diff --git a/tests/rest/client/test_presence.py b/tests/rest/client/test_presence.py
index 1d152352d..56fe1a3d0 100644
--- a/tests/rest/client/test_presence.py
+++ b/tests/rest/client/test_presence.py
@@ -50,7 +50,7 @@ def test_put_presence(self):
         PUT to the status endpoint with use_presence enabled will call
         set_state on the presence handler.
         """
-        self.hs.config.use_presence = True
+        self.hs.config.server.use_presence = True
 
         body = {"presence": "here", "status_msg": "beep boop"}
         channel = self.make_request(
diff --git a/tests/rest/client/test_register.py b/tests/rest/client/test_register.py
index 508b9b837..7a0248652 100644
--- a/tests/rest/client/test_register.py
+++ b/tests/rest/client/test_register.py
@@ -65,7 +65,7 @@ def test_POST_appservice_registration_valid(self):
 
         appservice = ApplicationService(
             as_token,
-            self.hs.config.server_name,
+            self.hs.config.server.server_name,
             id="1234",
             namespaces={"users": [{"regex": r"@as_user.*", "exclusive": True}]},
             sender="@as:test",
@@ -89,7 +89,7 @@ def test_POST_appservice_registration_no_type(self):
 
         appservice = ApplicationService(
             as_token,
-            self.hs.config.server_name,
+            self.hs.config.server.server_name,
             id="1234",
             namespaces={"users": [{"regex": r"@as_user.*", "exclusive": True}]},
             sender="@as:test",
@@ -155,7 +155,7 @@ def test_POST_disabled_registration(self):
 
     def test_POST_guest_registration(self):
         self.hs.config.key.macaroon_secret_key = "test"
-        self.hs.config.allow_guest_access = True
+        self.hs.config.registration.allow_guest_access = True
 
         channel = self.make_request(b"POST", self.url + b"?kind=guest", b"{}")
 
@@ -164,7 +164,7 @@ def test_POST_guest_registration(self):
         self.assertDictContainsSubset(det_data, channel.json_body)
 
     def test_POST_disabled_guest_registration(self):
-        self.hs.config.allow_guest_access = False
+        self.hs.config.registration.allow_guest_access = False
 
         channel = self.make_request(b"POST", self.url + b"?kind=guest", b"{}")
 
diff --git a/tests/rest/client/utils.py b/tests/rest/client/utils.py
index 3075d3f28..71fa87ce9 100644
--- a/tests/rest/client/utils.py
+++ b/tests/rest/client/utils.py
@@ -48,7 +48,7 @@ class RestHelper:
     def create_room_as(
         self,
         room_creator: Optional[str] = None,
-        is_public: bool = True,
+        is_public: Optional[bool] = None,
         room_version: Optional[str] = None,
         tok: Optional[str] = None,
         expect_code: int = 200,
@@ -62,9 +62,10 @@ def create_room_as(
 
         Args:
             room_creator: The user ID to create the room with.
-            is_public: If True, the `visibility` parameter will be set to the
-                default (public). Otherwise, the `visibility` parameter will be set
-                to "private".
+            is_public: If True, the `visibility` parameter will be set to
+                "public". If False, it will be set to "private". If left
+                unspecified, the server will set it to an appropriate default
+                (which should be "private" as per the CS spec).
             room_version: The room version to create the room as. Defaults to Synapse's
                 default room version.
             tok: The access token to use in the request.
@@ -77,8 +78,8 @@ def create_room_as(
         self.auth_user_id = room_creator
         path = "/_matrix/client/r0/createRoom"
         content = extra_content or {}
-        if not is_public:
-            content["visibility"] = "private"
+        if is_public is not None:
+            content["visibility"] = "public" if is_public else "private"
         if room_version:
             content["room_version"] = room_version
         if tok:
diff --git a/tests/rest/media/v1/test_url_preview.py b/tests/rest/media/v1/test_url_preview.py
index 4d09b5d07..8698135a7 100644
--- a/tests/rest/media/v1/test_url_preview.py
+++ b/tests/rest/media/v1/test_url_preview.py
@@ -21,11 +21,13 @@
 from twisted.test.proto_helpers import AccumulatingProtocol
 
 from synapse.config.oembed import OEmbedEndpointConfig
+from synapse.rest.media.v1.preview_url_resource import IMAGE_CACHE_EXPIRY_MS
 from synapse.util.stringutils import parse_and_validate_mxc_uri
 
 from tests import unittest
 from tests.server import FakeTransport
 from tests.test_utils import SMALL_PNG
+from tests.utils import MockClock
 
 try:
     import lxml
@@ -723,9 +725,107 @@ def test_oembed_format(self):
             },
         )
 
+    def test_oembed_autodiscovery(self):
+        """
+        Autodiscovery works by finding the link in the HTML response and then requesting an oEmbed URL.
+        1. Request a preview of a URL which is not known to the oEmbed code.
+        2. It returns HTML including a link to an oEmbed preview.
+        3. The oEmbed preview is requested and returns a URL for an image.
+        4. The image is requested for thumbnailing.
+        """
+        # This is a little cheesy in that we use the www subdomain (which isn't the
+        # list of oEmbed patterns) to get "raw" HTML response.
+        self.lookups["www.twitter.com"] = [(IPv4Address, "10.1.2.3")]
+        self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
+        self.lookups["cdn.twitter.com"] = [(IPv4Address, "10.1.2.3")]
+
+        result = b"""
+        <link rel="alternate" type="application/json+oembed"
+            href="http://publish.twitter.com/oembed?url=http%3A%2F%2Fcdn.twitter.com%2Fmatrixdotorg%2Fstatus%2F12345&format=json"
+            title="matrixdotorg" />
+        """
+
+        channel = self.make_request(
+            "GET",
+            "preview_url?url=http://www.twitter.com/matrixdotorg/status/12345",
+            shorthand=False,
+            await_result=False,
+        )
+        self.pump()
+
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b'Content-Type: text/html; charset="utf8"\r\n\r\n'
+            )
+            % (len(result),)
+            + result
+        )
+
+        self.pump()
+
+        # The oEmbed response.
+        result2 = {
+            "version": "1.0",
+            "type": "photo",
+            "url": "http://cdn.twitter.com/matrixdotorg",
+        }
+        oembed_content = json.dumps(result2).encode("utf-8")
+
+        # Ensure a second request is made to the oEmbed URL.
+        client = self.reactor.tcpClients[1][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b'Content-Type: application/json; charset="utf8"\r\n\r\n'
+            )
+            % (len(oembed_content),)
+            + oembed_content
+        )
+
+        self.pump()
+
+        # Ensure the URL is what was requested.
+        self.assertIn(b"/oembed?", server.data)
+
+        # Ensure a third request is made to the photo URL.
+        client = self.reactor.tcpClients[2][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b"Content-Type: image/png\r\n\r\n"
+            )
+            % (len(SMALL_PNG),)
+            + SMALL_PNG
+        )
+
+        self.pump()
+
+        # Ensure the URL is what was requested.
+        self.assertIn(b"/matrixdotorg", server.data)
+
+        self.assertEqual(channel.code, 200)
+        body = channel.json_body
+        self.assertEqual(
+            body["og:url"], "http://www.twitter.com/matrixdotorg/status/12345"
+        )
+        self.assertTrue(body["og:image"].startswith("mxc://"))
+        self.assertEqual(body["og:image:height"], 1)
+        self.assertEqual(body["og:image:width"], 1)
+        self.assertEqual(body["og:image:type"], "image/png")
+
     def _download_image(self):
         """Downloads an image into the URL cache.
-
         Returns:
             A (host, media_id) tuple representing the MXC URI of the image.
         """
@@ -851,3 +951,32 @@ def test_storage_providers_exclude_thumbnails(self):
             404,
             "URL cache thumbnail was unexpectedly retrieved from a storage provider",
         )
+
+    def test_cache_expiry(self):
+        """Test that URL cache files and thumbnails are cleaned up properly on expiry."""
+        self.preview_url.clock = MockClock()
+
+        _host, media_id = self._download_image()
+
+        file_path = self.preview_url.filepaths.url_cache_filepath(media_id)
+        file_dirs = self.preview_url.filepaths.url_cache_filepath_dirs_to_delete(
+            media_id
+        )
+        thumbnail_dir = self.preview_url.filepaths.url_cache_thumbnail_directory(
+            media_id
+        )
+        thumbnail_dirs = self.preview_url.filepaths.url_cache_thumbnail_dirs_to_delete(
+            media_id
+        )
+
+        self.assertTrue(os.path.isfile(file_path))
+        self.assertTrue(os.path.isdir(thumbnail_dir))
+
+        self.preview_url.clock.advance_time_msec(IMAGE_CACHE_EXPIRY_MS + 1)
+        self.get_success(self.preview_url._expire_url_cache_data())
+
+        for path in [file_path] + file_dirs + [thumbnail_dir] + thumbnail_dirs:
+            self.assertFalse(
+                os.path.exists(path),
+                f"{os.path.relpath(path, self.media_store_path)} was not deleted",
+            )
diff --git a/tests/server.py b/tests/server.py
index 88dfa8058..64645651c 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -317,7 +317,7 @@ class ThreadedMemoryReactorClock(MemoryReactorClock):
     def __init__(self):
         self.threadpool = ThreadPool(self)
 
-        self._tcp_callbacks = {}
+        self._tcp_callbacks: Dict[Tuple[str, int], Callable] = {}
         self._udp = []
         self.lookups: Dict[str, str] = {}
         self._thread_callbacks: Deque[Callable[[], None]] = deque()
@@ -355,7 +355,7 @@ def callFromThread(self, callback, *args, **kwargs):
     def getThreadPool(self):
         return self.threadpool
 
-    def add_tcp_client_callback(self, host, port, callback):
+    def add_tcp_client_callback(self, host: str, port: int, callback: Callable):
         """Add a callback that will be invoked when we receive a connection
         attempt to the given IP/port using `connectTCP`.
 
@@ -364,7 +364,7 @@ def add_tcp_client_callback(self, host, port, callback):
         """
         self._tcp_callbacks[(host, port)] = callback
 
-    def connectTCP(self, host, port, factory, timeout=30, bindAddress=None):
+    def connectTCP(self, host: str, port: int, factory, timeout=30, bindAddress=None):
         """Fake L{IReactorTCP.connectTCP}."""
 
         conn = super().connectTCP(
@@ -475,7 +475,7 @@ def runInteraction(interaction, *args, **kwargs):
     return server
 
 
-def get_clock():
+def get_clock() -> Tuple[ThreadedMemoryReactorClock, Clock]:
     clock = ThreadedMemoryReactorClock()
     hs_clock = Clock(clock)
     return clock, hs_clock
diff --git a/tests/server_notices/test_resource_limits_server_notices.py b/tests/server_notices/test_resource_limits_server_notices.py
index 7f25200a5..36c495954 100644
--- a/tests/server_notices/test_resource_limits_server_notices.py
+++ b/tests/server_notices/test_resource_limits_server_notices.py
@@ -346,7 +346,7 @@ def _trigger_notice_and_join(self):
         invites = []
 
         # Register as many users as the MAU limit allows.
-        for i in range(self.hs.config.max_mau_value):
+        for i in range(self.hs.config.server.max_mau_value):
             localpart = "user%d" % i
             user_id = self.register_user(localpart, "password")
             tok = self.login(localpart, "password")
diff --git a/tests/storage/databases/main/test_room.py b/tests/storage/databases/main/test_room.py
index ffee70715..7496974da 100644
--- a/tests/storage/databases/main/test_room.py
+++ b/tests/storage/databases/main/test_room.py
@@ -79,12 +79,7 @@ def test_background_populate_rooms_creator_column(self):
         self.store.db_pool.updates._all_done = False
 
         # Now let's actually drive the updates to completion
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         # Make sure the background update filled in the room creator
         room_creator_after = self.get_success(
diff --git a/tests/storage/test_appservice.py b/tests/storage/test_appservice.py
index cf9748f21..f26d5acf9 100644
--- a/tests/storage/test_appservice.py
+++ b/tests/storage/test_appservice.py
@@ -126,7 +126,7 @@ def setUp(self):
         self.db_pool = database._db_pool
         self.engine = database.engine
 
-        db_config = hs.config.get_single_database()
+        db_config = hs.config.database.get_single_database()
         self.store = TestTransactionStore(
             database, make_conn(db_config, self.engine, "test"), hs
         )
diff --git a/tests/storage/test_cleanup_extrems.py b/tests/storage/test_cleanup_extrems.py
index 7cc5e621b..a59c28f89 100644
--- a/tests/storage/test_cleanup_extrems.py
+++ b/tests/storage/test_cleanup_extrems.py
@@ -66,12 +66,7 @@ def run_delta_file(txn):
         # Ugh, have to reset this flag
         self.store.db_pool.updates._all_done = False
 
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
     def test_soft_failed_extremities_handled_correctly(self):
         """Test that extremities are correctly calculated in the presence of
diff --git a/tests/storage/test_client_ips.py b/tests/storage/test_client_ips.py
index 3cc8038f1..0e4013ebe 100644
--- a/tests/storage/test_client_ips.py
+++ b/tests/storage/test_client_ips.py
@@ -146,6 +146,49 @@ def test_insert_new_client_ip_none_device_id(self):
             ],
         )
 
+    @parameterized.expand([(False,), (True,)])
+    def test_get_last_client_ip_by_device(self, after_persisting: bool):
+        """Test `get_last_client_ip_by_device` for persisted and unpersisted data"""
+        self.reactor.advance(12345678)
+
+        user_id = "@user:id"
+        device_id = "MY_DEVICE"
+
+        # Insert a user IP
+        self.get_success(
+            self.store.store_device(
+                user_id,
+                device_id,
+                "display name",
+            )
+        )
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token", "ip", "user_agent", device_id
+            )
+        )
+
+        if after_persisting:
+            # Trigger the storage loop
+            self.reactor.advance(10)
+
+        result = self.get_success(
+            self.store.get_last_client_ip_by_device(user_id, device_id)
+        )
+
+        self.assertEqual(
+            result,
+            {
+                (user_id, device_id): {
+                    "user_id": user_id,
+                    "device_id": device_id,
+                    "ip": "ip",
+                    "user_agent": "user_agent",
+                    "last_seen": 12345678000,
+                },
+            },
+        )
+
     @parameterized.expand([(False,), (True,)])
     def test_get_user_ip_and_agents(self, after_persisting: bool):
         """Test `get_user_ip_and_agents` for persisted and unpersisted data"""
@@ -242,12 +285,7 @@ def test_updating_monthly_active_user_when_space(self):
 
     def test_devices_last_seen_bg_update(self):
         # First make sure we have completed all updates.
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         user_id = "@user:id"
         device_id = "MY_DEVICE"
@@ -311,12 +349,7 @@ def test_devices_last_seen_bg_update(self):
         self.store.db_pool.updates._all_done = False
 
         # Now let's actually drive the updates to completion
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         # We should now get the correct result again
         result = self.get_success(
@@ -337,12 +370,7 @@ def test_devices_last_seen_bg_update(self):
 
     def test_old_user_ips_pruned(self):
         # First make sure we have completed all updates.
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         user_id = "@user:id"
         device_id = "MY_DEVICE"
diff --git a/tests/storage/test_event_chain.py b/tests/storage/test_event_chain.py
index 93136f071..b31c5eb5e 100644
--- a/tests/storage/test_event_chain.py
+++ b/tests/storage/test_event_chain.py
@@ -578,12 +578,7 @@ def test_background_update_single_room(self):
         # Ugh, have to reset this flag
         self.store.db_pool.updates._all_done = False
 
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         # Test that the `has_auth_chain_index` has been set
         self.assertTrue(self.get_success(self.store.has_auth_chain_index(room_id)))
@@ -619,12 +614,7 @@ def test_background_update_multiple_rooms(self):
         # Ugh, have to reset this flag
         self.store.db_pool.updates._all_done = False
 
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         # Test that the `has_auth_chain_index` has been set
         self.assertTrue(self.get_success(self.store.has_auth_chain_index(room_id1)))
diff --git a/tests/storage/test_monthly_active_users.py b/tests/storage/test_monthly_active_users.py
index 944dbc34a..d6b4cdd78 100644
--- a/tests/storage/test_monthly_active_users.py
+++ b/tests/storage/test_monthly_active_users.py
@@ -51,7 +51,7 @@ def prepare(self, reactor, clock, homeserver):
 
     @override_config({"max_mau_value": 3, "mau_limit_reserved_threepids": gen_3pids(3)})
     def test_initialise_reserved_users(self):
-        threepids = self.hs.config.mau_limits_reserved_threepids
+        threepids = self.hs.config.server.mau_limits_reserved_threepids
 
         # register three users, of which two have reserved 3pids, and a third
         # which is a support user.
@@ -101,9 +101,9 @@ def test_initialise_reserved_users(self):
         # XXX some of this is redundant. poking things into the config shouldn't
         # work, and in any case it's not obvious what we expect to happen when
         # we advance the reactor.
-        self.hs.config.max_mau_value = 0
+        self.hs.config.server.max_mau_value = 0
         self.reactor.advance(FORTY_DAYS)
-        self.hs.config.max_mau_value = 5
+        self.hs.config.server.max_mau_value = 5
 
         self.get_success(self.store.reap_monthly_active_users())
 
@@ -183,7 +183,7 @@ def test_reap_monthly_active_users(self):
         self.get_success(d)
 
         count = self.get_success(self.store.get_monthly_active_count())
-        self.assertEqual(count, self.hs.config.max_mau_value)
+        self.assertEqual(count, self.hs.config.server.max_mau_value)
 
         self.reactor.advance(FORTY_DAYS)
 
@@ -199,7 +199,7 @@ def test_reap_monthly_active_users(self):
     def test_reap_monthly_active_users_reserved_users(self):
         """Tests that reaping correctly handles reaping where reserved users are
         present"""
-        threepids = self.hs.config.mau_limits_reserved_threepids
+        threepids = self.hs.config.server.mau_limits_reserved_threepids
         initial_users = len(threepids)
         reserved_user_number = initial_users - 1
         for i in range(initial_users):
@@ -234,7 +234,7 @@ def test_reap_monthly_active_users_reserved_users(self):
         self.get_success(d)
 
         count = self.get_success(self.store.get_monthly_active_count())
-        self.assertEqual(count, self.hs.config.max_mau_value)
+        self.assertEqual(count, self.hs.config.server.max_mau_value)
 
     def test_populate_monthly_users_is_guest(self):
         # Test that guest users are not added to mau list
@@ -294,7 +294,7 @@ def test_get_reserved_real_user_account(self):
             {"medium": "email", "address": user2_email},
         ]
 
-        self.hs.config.mau_limits_reserved_threepids = threepids
+        self.hs.config.server.mau_limits_reserved_threepids = threepids
         d = self.store.db_pool.runInteraction(
             "initialise", self.store._initialise_reserved_users, threepids
         )
diff --git a/tests/storage/test_roommember.py b/tests/storage/test_roommember.py
index c72dc4051..2873e22cc 100644
--- a/tests/storage/test_roommember.py
+++ b/tests/storage/test_roommember.py
@@ -169,12 +169,7 @@ def prepare(self, reactor, clock, homeserver):
 
     def test_can_rerun_update(self):
         # First make sure we have completed all updates.
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
 
         # Now let's create a room, which will insert a membership
         user = UserID("alice", "test")
@@ -197,9 +192,4 @@ def test_can_rerun_update(self):
         self.store.db_pool.updates._all_done = False
 
         # Now let's actually drive the updates to completion
-        while not self.get_success(
-            self.store.db_pool.updates.has_completed_background_updates()
-        ):
-            self.get_success(
-                self.store.db_pool.updates.do_next_background_update(100), by=0.1
-            )
+        self.wait_for_background_updates()
diff --git a/tests/storage/test_state.py b/tests/storage/test_state.py
index 32060f2ab..70d52b088 100644
--- a/tests/storage/test_state.py
+++ b/tests/storage/test_state.py
@@ -21,7 +21,7 @@
 from synapse.storage.state import StateFilter
 from synapse.types import RoomID, UserID
 
-from tests.unittest import HomeserverTestCase
+from tests.unittest import HomeserverTestCase, TestCase
 
 logger = logging.getLogger(__name__)
 
@@ -105,7 +105,6 @@ def test_get_state_groups(self):
         self.assertEqual({ev.event_id for ev in state_list}, {e1.event_id, e2.event_id})
 
     def test_get_state_for_event(self):
-
         # this defaults to a linear DAG as each new injection defaults to whatever
         # forward extremities are currently in the DB for this room.
         e1 = self.inject_state_event(self.room, self.u_alice, EventTypes.Create, "", {})
@@ -483,3 +482,513 @@ def test_get_state_for_event(self):
 
         self.assertEqual(is_all, True)
         self.assertDictEqual({(e5.type, e5.state_key): e5.event_id}, state_dict)
+
+
+class StateFilterDifferenceTestCase(TestCase):
+    def assert_difference(
+        self, minuend: StateFilter, subtrahend: StateFilter, expected: StateFilter
+    ):
+        self.assertEqual(
+            minuend.approx_difference(subtrahend),
+            expected,
+            f"StateFilter difference not correct:\n\n\t{minuend!r}\nminus\n\t{subtrahend!r}\nwas\n\t{minuend.approx_difference(subtrahend)}\nexpected\n\t{expected}",
+        )
+
+    def test_state_filter_difference_no_include_other_minus_no_include_other(self):
+        """
+        Tests the StateFilter.approx_difference method
+        where, in a.approx_difference(b), both a and b do not have the
+        include_others flag set.
+        """
+        # (wildcard on state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.Create: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.CanonicalAlias: None},
+                include_others=False,
+            ),
+            StateFilter.freeze({EventTypes.Create: None}, include_others=False),
+        )
+
+        # (wildcard on state keys) - (specific state keys)
+        # This one is an over-approximation because we can't represent
+        # 'all state keys except a few named examples'
+        self.assert_difference(
+            StateFilter.freeze({EventTypes.Member: None}, include_others=False),
+            StateFilter.freeze(
+                {EventTypes.Member: {"@wombat:spqr"}},
+                include_others=False,
+            ),
+            StateFilter.freeze({EventTypes.Member: None}, include_others=False),
+        )
+
+        # (wildcard on state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {EventTypes.CanonicalAlias: {""}},
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (specific state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr"},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+        )
+
+    def test_state_filter_difference_include_other_minus_no_include_other(self):
+        """
+        Tests the StateFilter.approx_difference method
+        where, in a.approx_difference(b), only a has the include_others flag set.
+        """
+        # (wildcard on state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.Create: None},
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.CanonicalAlias: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Create: None,
+                    EventTypes.Member: set(),
+                    EventTypes.CanonicalAlias: set(),
+                },
+                include_others=True,
+            ),
+        )
+
+        # (wildcard on state keys) - (specific state keys)
+        # This one is an over-approximation because we can't represent
+        # 'all state keys except a few named examples'
+        # This also shows that the resultant state filter is normalised.
+        self.assert_difference(
+            StateFilter.freeze({EventTypes.Member: None}, include_others=True),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr"},
+                    EventTypes.Create: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter(types=frozendict(), include_others=True),
+        )
+
+        # (wildcard on state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=False,
+            ),
+            StateFilter(
+                types=frozendict(),
+                include_others=True,
+            ),
+        )
+
+        # (specific state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.CanonicalAlias: {""},
+                    EventTypes.Member: set(),
+                },
+                include_others=True,
+            ),
+        )
+
+        # (specific state keys) - (specific state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr"},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+        )
+
+        # (specific state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+        )
+
+    def test_state_filter_difference_include_other_minus_include_other(self):
+        """
+        Tests the StateFilter.approx_difference method
+        where, in a.approx_difference(b), both a and b have the include_others
+        flag set.
+        """
+        # (wildcard on state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.Create: None},
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.CanonicalAlias: None},
+                include_others=True,
+            ),
+            StateFilter(types=frozendict(), include_others=False),
+        )
+
+        # (wildcard on state keys) - (specific state keys)
+        # This one is an over-approximation because we can't represent
+        # 'all state keys except a few named examples'
+        self.assert_difference(
+            StateFilter.freeze({EventTypes.Member: None}, include_others=True),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.CanonicalAlias: None},
+                include_others=False,
+            ),
+        )
+
+        # (wildcard on state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=True,
+            ),
+            StateFilter(
+                types=frozendict(),
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (specific state keys)
+        # This one is an over-approximation because we can't represent
+        # 'all state keys except a few named examples'
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                    EventTypes.Create: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr"},
+                    EventTypes.Create: set(),
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@spqr:spqr"},
+                    EventTypes.Create: {""},
+                },
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                },
+                include_others=False,
+            ),
+        )
+
+    def test_state_filter_difference_no_include_other_minus_include_other(self):
+        """
+        Tests the StateFilter.approx_difference method
+        where, in a.approx_difference(b), only b has the include_others flag set.
+        """
+        # (wildcard on state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.Create: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None, EventTypes.CanonicalAlias: None},
+                include_others=True,
+            ),
+            StateFilter(types=frozendict(), include_others=False),
+        )
+
+        # (wildcard on state keys) - (specific state keys)
+        # This one is an over-approximation because we can't represent
+        # 'all state keys except a few named examples'
+        self.assert_difference(
+            StateFilter.freeze({EventTypes.Member: None}, include_others=False),
+            StateFilter.freeze(
+                {EventTypes.Member: {"@wombat:spqr"}},
+                include_others=True,
+            ),
+            StateFilter.freeze({EventTypes.Member: None}, include_others=False),
+        )
+
+        # (wildcard on state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (wildcard on state keys):
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {EventTypes.Member: None},
+                include_others=True,
+            ),
+            StateFilter(
+                types=frozendict(),
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (specific state keys)
+        # This one is an over-approximation because we can't represent
+        # 'all state keys except a few named examples'
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr"},
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@spqr:spqr"},
+                },
+                include_others=False,
+            ),
+        )
+
+        # (specific state keys) - (no state keys)
+        self.assert_difference(
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                    EventTypes.CanonicalAlias: {""},
+                },
+                include_others=False,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: set(),
+                },
+                include_others=True,
+            ),
+            StateFilter.freeze(
+                {
+                    EventTypes.Member: {"@wombat:spqr", "@spqr:spqr"},
+                },
+                include_others=False,
+            ),
+        )
+
+    def test_state_filter_difference_simple_cases(self):
+        """
+        Tests some very simple cases of the StateFilter approx_difference,
+        that are not explicitly tested by the more in-depth tests.
+        """
+
+        self.assert_difference(StateFilter.all(), StateFilter.all(), StateFilter.none())
+
+        self.assert_difference(
+            StateFilter.all(),
+            StateFilter.none(),
+            StateFilter.all(),
+        )
diff --git a/tests/storage/test_txn_limit.py b/tests/storage/test_txn_limit.py
index 6ff3ebb13..ace82cbf4 100644
--- a/tests/storage/test_txn_limit.py
+++ b/tests/storage/test_txn_limit.py
@@ -22,7 +22,7 @@ def make_homeserver(self, reactor, clock):
         return self.setup_test_homeserver(db_txn_limit=1000)
 
     def test_config(self):
-        db_config = self.hs.config.get_single_database()
+        db_config = self.hs.config.database.get_single_database()
         self.assertEqual(db_config.config["txn_limit"], 1000)
 
     def test_select(self):
diff --git a/tests/storage/test_user_directory.py b/tests/storage/test_user_directory.py
index 222e5d129..be3ed64f5 100644
--- a/tests/storage/test_user_directory.py
+++ b/tests/storage/test_user_directory.py
@@ -11,7 +11,22 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from typing import Any, Dict, List, Set, Tuple
+from unittest import mock
+from unittest.mock import Mock, patch
 
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.api.constants import EventTypes, Membership, UserTypes
+from synapse.appservice import ApplicationService
+from synapse.rest import admin
+from synapse.rest.client import login, register, room
+from synapse.server import HomeServer
+from synapse.storage import DataStore
+from synapse.storage.roommember import ProfileInfo
+from synapse.util import Clock
+
+from tests.test_utils.event_injection import inject_member_event
 from tests.unittest import HomeserverTestCase, override_config
 
 ALICE = "@alice:a"
@@ -21,8 +36,391 @@
 BELA = "@somenickname:a"
 
 
+class GetUserDirectoryTables:
+    """Helper functions that we want to reuse in tests/handlers/test_user_directory.py"""
+
+    def __init__(self, store: DataStore):
+        self.store = store
+
+    def _compress_shared(
+        self, shared: List[Dict[str, str]]
+    ) -> Set[Tuple[str, str, str]]:
+        """
+        Compress a list of users who share rooms dicts to a list of tuples.
+        """
+        r = set()
+        for i in shared:
+            r.add((i["user_id"], i["other_user_id"], i["room_id"]))
+        return r
+
+    async def get_users_in_public_rooms(self) -> List[Tuple[str, str]]:
+        """Fetch the entire `users_in_public_rooms` table.
+
+        Returns a list of tuples (user_id, room_id) where room_id is public and
+        contains the user with the given id.
+        """
+        r = await self.store.db_pool.simple_select_list(
+            "users_in_public_rooms", None, ("user_id", "room_id")
+        )
+
+        retval = []
+        for i in r:
+            retval.append((i["user_id"], i["room_id"]))
+        return retval
+
+    async def get_users_who_share_private_rooms(self) -> List[Dict[str, str]]:
+        """Fetch the entire `users_who_share_private_rooms` table.
+
+        Returns a dict containing "user_id", "other_user_id" and "room_id" keys.
+        The dicts can be flattened to Tuples with the `_compress_shared` method.
+        (This seems a little awkward---maybe we could clean this up.)
+        """
+
+        return await self.store.db_pool.simple_select_list(
+            "users_who_share_private_rooms",
+            None,
+            ["user_id", "other_user_id", "room_id"],
+        )
+
+    async def get_users_in_user_directory(self) -> Set[str]:
+        """Fetch the set of users in the `user_directory` table.
+
+        This is useful when checking we've correctly excluded users from the directory.
+        """
+        result = await self.store.db_pool.simple_select_list(
+            "user_directory",
+            None,
+            ["user_id"],
+        )
+        return {row["user_id"] for row in result}
+
+    async def get_profiles_in_user_directory(self) -> Dict[str, ProfileInfo]:
+        """Fetch users and their profiles from the `user_directory` table.
+
+        This is useful when we want to inspect display names and avatars.
+        It's almost the entire contents of the `user_directory` table: the only
+        thing missing is an unused room_id column.
+        """
+        rows = await self.store.db_pool.simple_select_list(
+            "user_directory",
+            None,
+            ("user_id", "display_name", "avatar_url"),
+        )
+        return {
+            row["user_id"]: ProfileInfo(
+                display_name=row["display_name"], avatar_url=row["avatar_url"]
+            )
+            for row in rows
+        }
+
+
+class UserDirectoryInitialPopulationTestcase(HomeserverTestCase):
+    """Ensure that rebuilding the directory writes the correct data to the DB.
+
+    See also tests/handlers/test_user_directory.py for similar checks. They
+    test the incremental updates, rather than the big rebuild.
+    """
+
+    servlets = [
+        login.register_servlets,
+        admin.register_servlets,
+        room.register_servlets,
+        register.register_servlets,
+    ]
+
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
+        self.appservice = ApplicationService(
+            token="i_am_an_app_service",
+            hostname="test",
+            id="1234",
+            namespaces={"users": [{"regex": r"@as_user.*", "exclusive": True}]},
+            sender="@as:test",
+        )
+
+        mock_load_appservices = Mock(return_value=[self.appservice])
+        with patch(
+            "synapse.storage.databases.main.appservice.load_appservices",
+            mock_load_appservices,
+        ):
+            hs = super().make_homeserver(reactor, clock)
+        return hs
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self.store = hs.get_datastore()
+        self.user_dir_helper = GetUserDirectoryTables(self.store)
+
+    def _purge_and_rebuild_user_dir(self) -> None:
+        """Nuke the user directory tables, start the background process to
+        repopulate them, and wait for the process to complete. This allows us
+        to inspect the outcome of the background process alone, without any of
+        the other incremental updates.
+        """
+        self.get_success(self.store.update_user_directory_stream_pos(None))
+        self.get_success(self.store.delete_all_from_user_dir())
+
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
+
+        # Nothing updated yet
+        self.assertEqual(shares_private, [])
+        self.assertEqual(public_users, [])
+
+        # Ugh, have to reset this flag
+        self.store.db_pool.updates._all_done = False
+
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "populate_user_directory_createtables",
+                    "progress_json": "{}",
+                },
+            )
+        )
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "populate_user_directory_process_rooms",
+                    "progress_json": "{}",
+                    "depends_on": "populate_user_directory_createtables",
+                },
+            )
+        )
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "populate_user_directory_process_users",
+                    "progress_json": "{}",
+                    "depends_on": "populate_user_directory_process_rooms",
+                },
+            )
+        )
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "populate_user_directory_cleanup",
+                    "progress_json": "{}",
+                    "depends_on": "populate_user_directory_process_users",
+                },
+            )
+        )
+
+        self.wait_for_background_updates()
+
+    def test_initial(self) -> None:
+        """
+        The user directory's initial handler correctly updates the search tables.
+        """
+        u1 = self.register_user("user1", "pass")
+        u1_token = self.login(u1, "pass")
+        u2 = self.register_user("user2", "pass")
+        u2_token = self.login(u2, "pass")
+        u3 = self.register_user("user3", "pass")
+        u3_token = self.login(u3, "pass")
+
+        room = self.helper.create_room_as(u1, is_public=True, tok=u1_token)
+        self.helper.invite(room, src=u1, targ=u2, tok=u1_token)
+        self.helper.join(room, user=u2, tok=u2_token)
+
+        private_room = self.helper.create_room_as(u1, is_public=False, tok=u1_token)
+        self.helper.invite(private_room, src=u1, targ=u3, tok=u1_token)
+        self.helper.join(private_room, user=u3, tok=u3_token)
+
+        # Do the initial population of the user directory via the background update
+        self._purge_and_rebuild_user_dir()
+
+        shares_private = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        public_users = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
+
+        # User 1 and User 2 are in the same public room
+        self.assertEqual(set(public_users), {(u1, room), (u2, room)})
+
+        # User 1 and User 3 share private rooms
+        self.assertEqual(
+            self.user_dir_helper._compress_shared(shares_private),
+            {(u1, u3, private_room), (u3, u1, private_room)},
+        )
+
+        # All three should have entries in the directory
+        users = self.get_success(self.user_dir_helper.get_users_in_user_directory())
+        self.assertEqual(users, {u1, u2, u3})
+
+    # The next four tests (test_population_excludes_*) all set up
+    #   - A normal user included in the user dir
+    #   - A public and private room created by that user
+    #   - A user excluded from the room dir, belonging to both rooms
+
+    # They match similar logic in handlers/test_user_directory.py But that tests
+    # updating the directory; this tests rebuilding it from scratch.
+
+    def _create_rooms_and_inject_memberships(
+        self, creator: str, token: str, joiner: str
+    ) -> Tuple[str, str]:
+        """Create a public and private room as a normal user.
+        Then get the `joiner` into those rooms.
+        """
+        public_room = self.helper.create_room_as(
+            creator,
+            is_public=True,
+            # See https://github.com/matrix-org/synapse/issues/10951
+            extra_content={"visibility": "public"},
+            tok=token,
+        )
+        private_room = self.helper.create_room_as(creator, is_public=False, tok=token)
+
+        # HACK: get the user into these rooms
+        self.get_success(inject_member_event(self.hs, public_room, joiner, "join"))
+        self.get_success(inject_member_event(self.hs, private_room, joiner, "join"))
+
+        return public_room, private_room
+
+    def _check_room_sharing_tables(
+        self, normal_user: str, public_room: str, private_room: str
+    ) -> None:
+        # After rebuilding the directory, we should only see the normal user.
+        users = self.get_success(self.user_dir_helper.get_users_in_user_directory())
+        self.assertEqual(users, {normal_user})
+        in_public_rooms = self.get_success(
+            self.user_dir_helper.get_users_in_public_rooms()
+        )
+        self.assertEqual(set(in_public_rooms), {(normal_user, public_room)})
+        in_private_rooms = self.get_success(
+            self.user_dir_helper.get_users_who_share_private_rooms()
+        )
+        self.assertEqual(in_private_rooms, [])
+
+    def test_population_excludes_support_user(self) -> None:
+        # Create a normal and support user.
+        user = self.register_user("user", "pass")
+        token = self.login(user, "pass")
+        support = "@support1:test"
+        self.get_success(
+            self.store.register_user(
+                user_id=support, password_hash=None, user_type=UserTypes.SUPPORT
+            )
+        )
+
+        # Join the support user to rooms owned by the normal user.
+        public, private = self._create_rooms_and_inject_memberships(
+            user, token, support
+        )
+
+        # Rebuild the directory.
+        self._purge_and_rebuild_user_dir()
+
+        # Check the support user is not in the directory.
+        self._check_room_sharing_tables(user, public, private)
+
+    def test_population_excludes_deactivated_user(self) -> None:
+        user = self.register_user("naughty", "pass")
+        admin = self.register_user("admin", "pass", admin=True)
+        admin_token = self.login(admin, "pass")
+
+        # Deactivate the user.
+        channel = self.make_request(
+            "PUT",
+            f"/_synapse/admin/v2/users/{user}",
+            access_token=admin_token,
+            content={"deactivated": True},
+        )
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(channel.json_body["deactivated"], True)
+
+        # Join the deactivated user to rooms owned by the admin.
+        # Is this something that could actually happen outside of a test?
+        public, private = self._create_rooms_and_inject_memberships(
+            admin, admin_token, user
+        )
+
+        # Rebuild the user dir. The deactivated user should be missing.
+        self._purge_and_rebuild_user_dir()
+        self._check_room_sharing_tables(admin, public, private)
+
+    def test_population_excludes_appservice_user(self) -> None:
+        # Register an AS user.
+        user = self.register_user("user", "pass")
+        token = self.login(user, "pass")
+        as_user = self.register_appservice_user("as_user_potato", self.appservice.token)
+
+        # Join the AS user to rooms owned by the normal user.
+        public, private = self._create_rooms_and_inject_memberships(
+            user, token, as_user
+        )
+
+        # Rebuild the directory.
+        self._purge_and_rebuild_user_dir()
+
+        # Check the AS user is not in the directory.
+        self._check_room_sharing_tables(user, public, private)
+
+    def test_population_excludes_appservice_sender(self) -> None:
+        user = self.register_user("user", "pass")
+        token = self.login(user, "pass")
+
+        # Join the AS sender to rooms owned by the normal user.
+        public, private = self._create_rooms_and_inject_memberships(
+            user, token, self.appservice.sender
+        )
+
+        # Rebuild the directory.
+        self._purge_and_rebuild_user_dir()
+
+        # Check the AS sender is not in the directory.
+        self._check_room_sharing_tables(user, public, private)
+
+    def test_population_conceals_private_nickname(self) -> None:
+        # Make a private room, and set a nickname within
+        user = self.register_user("aaaa", "pass")
+        user_token = self.login(user, "pass")
+        private_room = self.helper.create_room_as(user, is_public=False, tok=user_token)
+        self.helper.send_state(
+            private_room,
+            EventTypes.Member,
+            state_key=user,
+            body={"membership": Membership.JOIN, "displayname": "BBBB"},
+            tok=user_token,
+        )
+
+        # Rebuild the user directory. Make the rescan of the `users` table a no-op
+        # so we only see the effect of scanning the `room_memberships` table.
+        async def mocked_process_users(*args: Any, **kwargs: Any) -> int:
+            await self.store.db_pool.updates._end_background_update(
+                "populate_user_directory_process_users"
+            )
+            return 1
+
+        with mock.patch.dict(
+            self.store.db_pool.updates._background_update_handlers,
+            populate_user_directory_process_users=mocked_process_users,
+        ):
+            self._purge_and_rebuild_user_dir()
+
+        # Local users are ignored by the scan over rooms
+        users = self.get_success(self.user_dir_helper.get_profiles_in_user_directory())
+        self.assertEqual(users, {})
+
+        # Do a full rebuild including the scan over the `users` table. The local
+        # user should appear with their profile name.
+        self._purge_and_rebuild_user_dir()
+        users = self.get_success(self.user_dir_helper.get_profiles_in_user_directory())
+        self.assertEqual(
+            users, {user: ProfileInfo(display_name="aaaa", avatar_url=None)}
+        )
+
+
 class UserDirectoryStoreTestCase(HomeserverTestCase):
-    def prepare(self, reactor, clock, hs):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.store = hs.get_datastore()
 
         # alice and bob are both in !room_id. bobby is not but shares
@@ -33,7 +431,7 @@ def prepare(self, reactor, clock, hs):
         self.get_success(self.store.update_profile_in_user_dir(BELA, "Bela", None))
         self.get_success(self.store.add_users_in_public_rooms("!room:id", (ALICE, BOB)))
 
-    def test_search_user_dir(self):
+    def test_search_user_dir(self) -> None:
         # normally when alice searches the directory she should just find
         # bob because bobby doesn't share a room with her.
         r = self.get_success(self.store.search_user_dir(ALICE, "bob", 10))
@@ -44,7 +442,7 @@ def test_search_user_dir(self):
         )
 
     @override_config({"user_directory": {"search_all_users": True}})
-    def test_search_user_dir_all_users(self):
+    def test_search_user_dir_all_users(self) -> None:
         r = self.get_success(self.store.search_user_dir(ALICE, "bob", 10))
         self.assertFalse(r["limited"])
         self.assertEqual(2, len(r["results"]))
@@ -58,7 +456,7 @@ def test_search_user_dir_all_users(self):
         )
 
     @override_config({"user_directory": {"search_all_users": True}})
-    def test_search_user_dir_stop_words(self):
+    def test_search_user_dir_stop_words(self) -> None:
         """Tests that a user can look up another user by searching for the start if its
         display name even if that name happens to be a common English word that would
         usually be ignored in full text searches.
diff --git a/tests/test_event_auth.py b/tests/test_event_auth.py
index 1a4d07878..cf407c51c 100644
--- a/tests/test_event_auth.py
+++ b/tests/test_event_auth.py
@@ -38,21 +38,19 @@ def test_random_users_cannot_send_state_before_first_pl(self):
         }
 
         # creator should be able to send state
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V1,
             _random_state_event(creator),
             auth_events,
-            do_sig_check=False,
         )
 
         # joiner should not be able to send state
         self.assertRaises(
             AuthError,
-            event_auth.check,
+            event_auth.check_auth_rules_for_event,
             RoomVersions.V1,
             _random_state_event(joiner),
             auth_events,
-            do_sig_check=False,
         )
 
     def test_state_default_level(self):
@@ -77,19 +75,17 @@ def test_state_default_level(self):
         # pleb should not be able to send state
         self.assertRaises(
             AuthError,
-            event_auth.check,
+            event_auth.check_auth_rules_for_event,
             RoomVersions.V1,
             _random_state_event(pleb),
             auth_events,
-            do_sig_check=False,
         ),
 
         # king should be able to send state
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V1,
             _random_state_event(king),
             auth_events,
-            do_sig_check=False,
         )
 
     def test_alias_event(self):
@@ -102,37 +98,33 @@ def test_alias_event(self):
         }
 
         # creator should be able to send aliases
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V1,
             _alias_event(creator),
             auth_events,
-            do_sig_check=False,
         )
 
         # Reject an event with no state key.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V1,
                 _alias_event(creator, state_key=""),
                 auth_events,
-                do_sig_check=False,
             )
 
         # If the domain of the sender does not match the state key, reject.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V1,
                 _alias_event(creator, state_key="test.com"),
                 auth_events,
-                do_sig_check=False,
             )
 
         # Note that the member does *not* need to be in the room.
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V1,
             _alias_event(other),
             auth_events,
-            do_sig_check=False,
         )
 
     def test_msc2432_alias_event(self):
@@ -145,34 +137,30 @@ def test_msc2432_alias_event(self):
         }
 
         # creator should be able to send aliases
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _alias_event(creator),
             auth_events,
-            do_sig_check=False,
         )
 
         # No particular checks are done on the state key.
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _alias_event(creator, state_key=""),
             auth_events,
-            do_sig_check=False,
         )
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _alias_event(creator, state_key="test.com"),
             auth_events,
-            do_sig_check=False,
         )
 
         # Per standard auth rules, the member must be in the room.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _alias_event(other),
                 auth_events,
-                do_sig_check=False,
             )
 
     def test_msc2209(self):
@@ -192,20 +180,18 @@ def test_msc2209(self):
         }
 
         # pleb should be able to modify the notifications power level.
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V1,
             _power_levels_event(pleb, {"notifications": {"room": 100}}),
             auth_events,
-            do_sig_check=False,
         )
 
         # But an MSC2209 room rejects this change.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _power_levels_event(pleb, {"notifications": {"room": 100}}),
                 auth_events,
-                do_sig_check=False,
             )
 
     def test_join_rules_public(self):
@@ -222,59 +208,53 @@ def test_join_rules_public(self):
         }
 
         # Check join.
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
         # A user cannot be force-joined to a room.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _member_event(pleb, "join", sender=creator),
                 auth_events,
-                do_sig_check=False,
             )
 
         # Banned should be rejected.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "ban")
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _join_event(pleb),
                 auth_events,
-                do_sig_check=False,
             )
 
         # A user who left can re-join.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "leave")
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
         # A user can send a join if they're in the room.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "join")
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
         # A user can accept an invite.
         auth_events[("m.room.member", pleb)] = _member_event(
             pleb, "invite", sender=creator
         )
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
     def test_join_rules_invite(self):
@@ -292,60 +272,54 @@ def test_join_rules_invite(self):
 
         # A join without an invite is rejected.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _join_event(pleb),
                 auth_events,
-                do_sig_check=False,
             )
 
         # A user cannot be force-joined to a room.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _member_event(pleb, "join", sender=creator),
                 auth_events,
-                do_sig_check=False,
             )
 
         # Banned should be rejected.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "ban")
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _join_event(pleb),
                 auth_events,
-                do_sig_check=False,
             )
 
         # A user who left cannot re-join.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "leave")
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _join_event(pleb),
                 auth_events,
-                do_sig_check=False,
             )
 
         # A user can send a join if they're in the room.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "join")
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
         # A user can accept an invite.
         auth_events[("m.room.member", pleb)] = _member_event(
             pleb, "invite", sender=creator
         )
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V6,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
     def test_join_rules_msc3083_restricted(self):
@@ -370,11 +344,10 @@ def test_join_rules_msc3083_restricted(self):
 
         # Older room versions don't understand this join rule
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V6,
                 _join_event(pleb),
                 auth_events,
-                do_sig_check=False,
             )
 
         # A properly formatted join event should work.
@@ -384,11 +357,10 @@ def test_join_rules_msc3083_restricted(self):
                 EventContentFields.AUTHORISING_USER: "@creator:example.com"
             },
         )
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V8,
             authorised_join_event,
             auth_events,
-            do_sig_check=False,
         )
 
         # A join issued by a specific user works (i.e. the power level checks
@@ -400,7 +372,7 @@ def test_join_rules_msc3083_restricted(self):
         pl_auth_events[("m.room.member", "@inviter:foo.test")] = _join_event(
             "@inviter:foo.test"
         )
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V8,
             _join_event(
                 pleb,
@@ -409,16 +381,14 @@ def test_join_rules_msc3083_restricted(self):
                 },
             ),
             pl_auth_events,
-            do_sig_check=False,
         )
 
         # A join which is missing an authorised server is rejected.
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V8,
                 _join_event(pleb),
                 auth_events,
-                do_sig_check=False,
             )
 
         # An join authorised by a user who is not in the room is rejected.
@@ -427,7 +397,7 @@ def test_join_rules_msc3083_restricted(self):
             creator, {"invite": 100, "users": {"@other:example.com": 150}}
         )
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V8,
                 _join_event(
                     pleb,
@@ -436,13 +406,12 @@ def test_join_rules_msc3083_restricted(self):
                     },
                 ),
                 auth_events,
-                do_sig_check=False,
             )
 
         # A user cannot be force-joined to a room. (This uses an event which
         # *would* be valid, but is sent be a different user.)
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V8,
                 _member_event(
                     pleb,
@@ -453,36 +422,32 @@ def test_join_rules_msc3083_restricted(self):
                     },
                 ),
                 auth_events,
-                do_sig_check=False,
             )
 
         # Banned should be rejected.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "ban")
         with self.assertRaises(AuthError):
-            event_auth.check(
+            event_auth.check_auth_rules_for_event(
                 RoomVersions.V8,
                 authorised_join_event,
                 auth_events,
-                do_sig_check=False,
             )
 
         # A user who left can re-join.
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "leave")
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V8,
             authorised_join_event,
             auth_events,
-            do_sig_check=False,
         )
 
         # A user can send a join if they're in the room. (This doesn't need to
         # be authorised since the user is already joined.)
         auth_events[("m.room.member", pleb)] = _member_event(pleb, "join")
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V8,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
         # A user can accept an invite. (This doesn't need to be authorised since
@@ -490,11 +455,10 @@ def test_join_rules_msc3083_restricted(self):
         auth_events[("m.room.member", pleb)] = _member_event(
             pleb, "invite", sender=creator
         )
-        event_auth.check(
+        event_auth.check_auth_rules_for_event(
             RoomVersions.V8,
             _join_event(pleb),
             auth_events,
-            do_sig_check=False,
         )
 
 
diff --git a/tests/test_federation.py b/tests/test_federation.py
index c51e018da..24fc77d7a 100644
--- a/tests/test_federation.py
+++ b/tests/test_federation.py
@@ -82,7 +82,6 @@ async def _check_event_auth(
             event,
             context,
             state=None,
-            claimed_auth_event_map=None,
             backfilled=False,
         ):
             return context
diff --git a/tests/test_mau.py b/tests/test_mau.py
index 66111eb36..c683c8937 100644
--- a/tests/test_mau.py
+++ b/tests/test_mau.py
@@ -13,11 +13,11 @@
 # limitations under the License.
 
 """Tests REST events for /rooms paths."""
-
+import synapse.rest.admin
 from synapse.api.constants import APP_SERVICE_REGISTRATION_TYPE, LoginType
 from synapse.api.errors import Codes, HttpResponseException, SynapseError
 from synapse.appservice import ApplicationService
-from synapse.rest.client import register, sync
+from synapse.rest.client import login, profile, register, sync
 
 from tests import unittest
 from tests.unittest import override_config
@@ -26,7 +26,13 @@
 
 class TestMauLimit(unittest.HomeserverTestCase):
 
-    servlets = [register.register_servlets, sync.register_servlets]
+    servlets = [
+        register.register_servlets,
+        sync.register_servlets,
+        synapse.rest.admin.register_servlets_for_client_rest_resource,
+        profile.register_servlets,
+        login.register_servlets,
+    ]
 
     def default_config(self):
         config = default_config("test")
@@ -165,7 +171,7 @@ def test_trial_delay(self):
 
     @override_config({"mau_trial_days": 1})
     def test_trial_users_cant_come_back(self):
-        self.hs.config.mau_trial_days = 1
+        self.hs.config.server.mau_trial_days = 1
 
         # We should be able to register more than the limit initially
         token1 = self.create_user("kermit1")
@@ -229,6 +235,31 @@ def test_tracked_but_not_limited(self):
         self.reactor.advance(100)
         self.assertEqual(2, self.successResultOf(count))
 
+    def test_deactivated_users_dont_count_towards_mau(self):
+        user1 = self.register_user("madonna", "password")
+        self.register_user("prince", "password2")
+        self.register_user("frodo", "onering", True)
+
+        token1 = self.login("madonna", "password")
+        token2 = self.login("prince", "password2")
+        admin_token = self.login("frodo", "onering")
+
+        self.do_sync_for_user(token1)
+        self.do_sync_for_user(token2)
+
+        # Check that mau count is what we expect
+        count = self.get_success(self.store.get_monthly_active_count())
+        self.assertEqual(count, 2)
+
+        # Deactivate user1
+        url = "/_synapse/admin/v1/deactivate/%s" % user1
+        channel = self.make_request("POST", url, access_token=admin_token)
+        self.assertIn("success", channel.json_body["id_server_unbind_result"])
+
+        # Check that deactivated user is no longer counted
+        count = self.get_success(self.store.get_monthly_active_count())
+        self.assertEqual(count, 1)
+
     def create_user(self, localpart, token=None, appservice=False):
         request_data = {
             "username": localpart,
diff --git a/tests/test_preview.py b/tests/test_preview.py
index 48e792b55..09e017b4d 100644
--- a/tests/test_preview.py
+++ b/tests/test_preview.py
@@ -13,7 +13,8 @@
 # limitations under the License.
 
 from synapse.rest.media.v1.preview_url_resource import (
-    decode_and_calc_og,
+    _calc_og,
+    decode_body,
     get_html_media_encoding,
     summarize_paragraphs,
 )
@@ -158,7 +159,8 @@ def test_simple(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
 
@@ -173,7 +175,8 @@ def test_comment(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
 
@@ -191,7 +194,8 @@ def test_comment2(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(
             og,
@@ -212,7 +216,8 @@ def test_script(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
 
@@ -225,7 +230,8 @@ def test_missing_title(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(og, {"og:title": None, "og:description": "Some text."})
 
@@ -239,7 +245,8 @@ def test_h1_as_title(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(og, {"og:title": "Title", "og:description": "Some text."})
 
@@ -253,21 +260,22 @@ def test_missing_title_and_broken_h1(self):
         </html>
         """
 
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
 
         self.assertEqual(og, {"og:title": None, "og:description": "Some text."})
 
     def test_empty(self):
         """Test a body with no data in it."""
         html = b""
-        og = decode_and_calc_og(html, "http://example.com/test.html")
-        self.assertEqual(og, {})
+        tree = decode_body(html)
+        self.assertIsNone(tree)
 
     def test_no_tree(self):
         """A valid body with no tree in it."""
         html = b"\x00"
-        og = decode_and_calc_og(html, "http://example.com/test.html")
-        self.assertEqual(og, {})
+        tree = decode_body(html)
+        self.assertIsNone(tree)
 
     def test_invalid_encoding(self):
         """An invalid character encoding should be ignored and treated as UTF-8, if possible."""
@@ -279,9 +287,8 @@ def test_invalid_encoding(self):
         </body>
         </html>
         """
-        og = decode_and_calc_og(
-            html, "http://example.com/test.html", "invalid-encoding"
-        )
+        tree = decode_body(html, "invalid-encoding")
+        og = _calc_og(tree, "http://example.com/test.html")
         self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
 
     def test_invalid_encoding2(self):
@@ -295,7 +302,8 @@ def test_invalid_encoding2(self):
         </body>
         </html>
         """
-        og = decode_and_calc_og(html, "http://example.com/test.html")
+        tree = decode_body(html)
+        og = _calc_og(tree, "http://example.com/test.html")
         self.assertEqual(og, {"og:title": "ÿÿ Foo", "og:description": "Some text."})
 
 
diff --git a/tests/unittest.py b/tests/unittest.py
index 7a6f5954d..81c1a9e9d 100644
--- a/tests/unittest.py
+++ b/tests/unittest.py
@@ -20,7 +20,7 @@
 import logging
 import secrets
 import time
-from typing import Callable, Dict, Iterable, Optional, Tuple, Type, TypeVar, Union
+from typing import Any, Callable, Dict, Iterable, Optional, Tuple, Type, TypeVar, Union
 from unittest.mock import Mock, patch
 
 from canonicaljson import json
@@ -28,6 +28,7 @@
 from twisted.internet.defer import Deferred, ensureDeferred, succeed
 from twisted.python.failure import Failure
 from twisted.python.threadpool import ThreadPool
+from twisted.test.proto_helpers import MemoryReactor
 from twisted.trial import unittest
 from twisted.web.resource import Resource
 
@@ -46,6 +47,7 @@
 )
 from synapse.server import HomeServer
 from synapse.types import UserID, create_requester
+from synapse.util import Clock
 from synapse.util.httpresourcetree import create_resource_tree
 from synapse.util.ratelimitutils import FederationRateLimiter
 
@@ -232,7 +234,7 @@ def setUp(self):
         # Honour the `use_frozen_dicts` config option. We have to do this
         # manually because this is taken care of in the app `start` code, which
         # we don't run. Plus we want to reset it on tearDown.
-        events.USE_FROZEN_DICTS = self.hs.config.use_frozen_dicts
+        events.USE_FROZEN_DICTS = self.hs.config.server.use_frozen_dicts
 
         if self.hs is None:
             raise Exception("No homeserver returned from make_homeserver.")
@@ -315,6 +317,15 @@ def wait_on_thread(self, deferred, timeout=10):
             self.reactor.advance(0.01)
             time.sleep(0.01)
 
+    def wait_for_background_updates(self) -> None:
+        """Block until all background database updates have completed."""
+        while not self.get_success(
+            self.store.db_pool.updates.has_completed_background_updates()
+        ):
+            self.get_success(
+                self.store.db_pool.updates.do_next_background_update(100), by=0.1
+            )
+
     def make_homeserver(self, reactor, clock):
         """
         Make and return a homeserver.
@@ -371,7 +382,7 @@ def default_config(self):
 
         return config
 
-    def prepare(self, reactor, clock, homeserver):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, homeserver: HomeServer):
         """
         Prepare for the test.  This involves things like mocking out parts of
         the homeserver, or building test data common across the whole test
@@ -447,7 +458,7 @@ def make_request(
             client_ip,
         )
 
-    def setup_test_homeserver(self, *args, **kwargs):
+    def setup_test_homeserver(self, *args: Any, **kwargs: Any) -> HomeServer:
         """
         Set up the test homeserver, meant to be called by the overridable
         make_homeserver. It automatically passes through the test class's
@@ -558,7 +569,7 @@ def register_user(
         Returns:
             The MXID of the new user.
         """
-        self.hs.config.registration_shared_secret = "shared"
+        self.hs.config.registration.registration_shared_secret = "shared"
 
         # Create the user
         channel = self.make_request("GET", "/_synapse/admin/v1/register")
@@ -594,6 +605,35 @@ def register_user(
         user_id = channel.json_body["user_id"]
         return user_id
 
+    def register_appservice_user(
+        self,
+        username: str,
+        appservice_token: str,
+    ) -> str:
+        """Register an appservice user as an application service.
+        Requires the client-facing registration API be registered.
+
+        Args:
+            username: the user to be registered by an application service.
+                Should be a full username, i.e. ""@localpart:hostname" as opposed to just "localpart"
+            appservice_token: the acccess token for that application service.
+
+        Raises: if the request to '/register' does not return 200 OK.
+
+        Returns: the MXID of the new user.
+        """
+        channel = self.make_request(
+            "POST",
+            "/_matrix/client/r0/register",
+            {
+                "username": username,
+                "type": "m.login.application_service",
+            },
+            access_token=appservice_token,
+        )
+        self.assertEqual(channel.code, 200, channel.json_body)
+        return channel.json_body["user_id"]
+
     def login(
         self,
         username,
diff --git a/tox.ini b/tox.ini
index d284d8860..be00f7914 100644
--- a/tox.ini
+++ b/tox.ini
@@ -41,10 +41,10 @@ lint_targets =
     scripts/hash_password
     scripts/register_new_matrix_user
     scripts/synapse_port_db
+    scripts/update_synapse_database
     scripts-dev
     scripts-dev/build_debian_packages
     scripts-dev/sign_json
-    scripts-dev/update_database
     stubs
     contrib
     synctl