Engineering interviews

This repository contains a folder with coding challenges I've been asked to solve during my application batches from 2023 and beyond, I'll do my best to keep it updated with fresh questions. This very readme file contains the guidelines I follow when I interview candidates for an Engineering role and part of my question pool, mixed with questions I got asked during interviews.

I have been a hiring manager for some time but I've also applied and got interviews for many companies (100+) - including AWS, Microsoft, Google, Uber, Booking.com and ClickHouse.

Note: for the sake of transparency I didn't got a job offer from these (yet) but with some I passed some of their coding and system interviews alike

My idea for this repo is, since I have seen and experienced first hand a lot of different approaches to the interview process, I want to provide some guideline for people to follow and maybe even spar with someone, or with me - for a (relatively) small fee.

The following list is a collection of unsorted questions that purposefully have no answers. The rationale is to use this as a reference for your own interview process (as candidate or as hiring manager) and to prepare for it.

Contributions to this code base are welcome but subject to my sole judgement for inclusion or exclusion, feel free to fork.

STAR Method

The STAR method S.T.A.R. is a useful acronym and an effective formula for structuring your interview responses for tech companies.

• Situation (20%), explain the situation so that your interviewer understands the context of your example, they do not need to know every technical detail.
• Task (10%), talk about the task that you took responsibility for completing or the goal of your efforts.
• Action (60%), describe the actions that you personally took to complete the task or reach the end goal. Highlight skills or character traits addressed in the question. Use a lot of "I" instead of "we".
• Result (10%), explain the positive outcomes or results generated by your actions or efforts. Here, it is important to highlight quantifiable results. You may also want to emphasize what you learned from the experience or your key takeaways. This can even be a not-so-pleasant experience, in that case still try to focus on positive takeaways.

Intro

• How are you doing/weather, something nice to break the ice and make the candidate feel comfortable
• Tell me about your engineering journey, how did you get into engineering?
• What do you like about this job?
• What are you looking for in your next role?
• What is your favorite programming language and why?
• What is the best piece of code you have ever written? And the worst?
• Do you hate PHP? (I do)
• Are you nervous? (I am)

General

Git

• What is the difference between a remote branch and a local branch?
• How can I delete a remote branch? Please give the command
• What’s a tag and how is it used?
• What’s a hook? Make an example of its use.
• What’s a submodule and when should it be used?
• How can I rollback the last commit I made on my local branch?
• Rebase vs merge, explain the difference and when to use one or the other

Network

• How does the TCP/IP protocol work?
• What’s a DNS and how does that work?
• What is a VPN?
• What is a NAT tunnel?
• How does DHCP work?
• What is a firewall? What is a WAF?
• How would you block a specific IP address from accessing a service?
• What is a proxy? What is a reverse proxy? What is a forward proxy?
• How does a load balancer work?
• Do you know any Load Balancing algorithms? Explain them (e.g. Round Robin, Least Connections, etc.)

Linux and Virtualization

• What is Linux and what makes it different from other operating systems?
• What is a directory?
• What’s "the kernel"?
• How can you install software on a Linux system and what are the common package managers used in Linux?
• What’s the command for changing the permission of a file? Give an example
• What’s the command for changing the ownership of a file? Give an example
• What’s a command for killing a process given its PID? Give an example
• What’s a command to list all the processes running? Give an example
• What’s the command, named after a protocol, to connect to a remote server in Linux? Give an example
• What’s a service in Linux?
• How does SELinux work?
• What does it happen when you launch $? in bash?
• What is a virtual machine (VM) and how does it work?
• What’s a hypervisor software?

DevOps, SRE and Platform Engineering

CI/CD

• What’s CI/CD?
• Explain the phases of CI/CD
• Have you ever used GitHub actions? How does it work?
• Have you ever used GitLab? How does it differ from GitHub?

Docker and Containerization

• What’s the difference between a virtual machine and a container runtime?
• How does containerization work?
• Is Docker the only way to create a container?
• What is the purpose and power of an image?
• What is the registry and how is it used in containerization?
• What’s a Dockerfile?
• What is the first line of a Dockerfile?
• How do you attach a volume in a Docker container?
• How do you manage or orchestrate multiple containers?
• What’s the purpose of Docker Compose?
• Best practice for building a good Dockerfile
• Why too many lines are bad for a Dockerfile?

Cloud

• What is cloud computing?
• Define public, hybrid, and private cloud and give a use case for each
• What is serverless?
• Is I say edge computing, what do I mean?
• List some CNCF (Cloud Native Computing Foundation) graduated projects or projects you like

Site Reliability Engineering

• What is a receiver in an alert manager?
• What happens when you execute a curl command on a Prometheus exporter endpoint?
• Give me an example of an OpenMetrics payload
• What is a Service Level Objective (SLO)?
• What is a Service Level Indicator (SLI)?
• What is a Service Level Agreement (SLA)?
• If I say "Error Budget", what do I mean? SLA is 99.9%, what is the error budget?

Terraform and Infrastructure as Code

• What is Infrastructure as Code and why is it important in modern cloud development?
• Explain the following commands: terraform init, terraform plan, terraform apply
• What is the purpose of the Terraform state file?
• What is Terraform's remote state?
• Where should it be stored, for example, in AWS as a cloud provider?
• What is a Terraform provider and what’s the difference between a provider and a resource?
• What is the way of reusing Terraform templates?
• How can you use Terraform variables?
• What major cloud provider can Terraform work with?
• How does Terraform handle updates to existing resources?
• How does Terraform handle dependencies between resources?

Kubernetes, Helm, and Container Orchestration

• What is Kubernetes, and what are some of its main features and benefits?
• What are the components of a Kubernetes cluster, and how do they interact with each other?
• How can you interact with Kubernetes API?
• Explain these commands: k create, k get, k describe, k delete, k apply, k logs, k exec, scale, rollout
• How do you create a Kubernetes deployment, and what are some best practices to follow when defining deployments?
• What is an ImagePullPolicy and what values can this parameter hold?
• What is a Kubernetes port forward? Why do you use that? What’s the command to perform that?
• NodePort vs LoadBalancer?
• What is the role of the Scheduler?
• Explain node affinity, node taints, node selectors, and pod priority.
• What are Kubernetes pods, and how do they relate to containers?
• Explain the Pod lifecycle
• What is the CrashLoopBackOff state?
• Explain the following command

kubectl run nginx --image=nginx:latest --port=80 --env="ENV_VAR=value" --labels="app=nginx" --
limits="cpu=500m,memory=256Mi" --requests="cpu=250m,memory=128Mi" --dry-run=client -o yaml > nginx.yaml

• What’s the difference between resource request and resource limit in Kubernetes?
• When is a Pod evicted?
• How does Kubernetes health checks work?
• What is a livenessProbe ?
• What is a readinessProbe ?
• What is a startupProbe ?
• How many kinds of probe types are there?
• NodeAffinity vs PodAffinity
• What is the POD disruption budget?
• What is a Kubernetes volume?
• How is a Kubernetes volume different from a container's file system?
• What are some types of Kubernetes volumes?
• How do you define a Kubernetes volume in a Pod's YAML configuration?
• How do you mount a Kubernetes volume to a container?
• Can multiple containers in a Pod share the same volume?
• What is a Persistent Volume (PV) in Kubernetes?
• How do you define a Persistent Volume in Kubernetes?
• How do you claim a Persistent Volume in Kubernetes (PVC)?
• How do you use a Persistent Volume in a Pod?
• What is a StorageClass and how does that work?
• What are the benefits of StorageClass?
• What is a Kubernetes namespace, and how can it be used to manage resources in a multi-tenant environment?
• What are Kubernetes Services, and how do they enable application discovery and load balancing?
• What is an Ingress and how does it work?
• What is a Kubernetes Controller and how does it work?
• Explain the difference between ReplicaSet controller, Deployment controller, StatefulSet controller, and DaemonSet controller
• What is a secret, and how can it be used to manage sensitive information like passwords and API keys?
• How do you scale a Kubernetes deployment, and what factors should you consider when determining the optimal number of replicas?
• Also, what metrics exist (natively) that can trigger a new pod?
• What kind of autoscaling is Kubernetes capable of?
• What is HPA and how does it work?
• What is Cluster Autoscaling and how does it work?
• What is a ConfigMap?
• What’s a Kubernetes Operator?
• Explain RBAC - Role Based Access Control
• What is the difference between Role and RoleBinding?
• Role vs ClusterRole, explain the difference
• What are some best practices for monitoring and logging Kubernetes clusters and applications running on them?
• Do you have any experience with Grafana+Prometheus, New Relic, Datadog, Dynatrace, or other similar products?
• How would you decide to separate Kubernetes clusters in an organisation? In what conditions would you have a single cluster?
• How do you manage multi-tenancy on Kubernetes in general and in terms of billing?
• How would you set up a high availability HA cluster in Kubernetes?
  • How would you manage etcd? Stacked or unstacked?

Helm

• What is Helm?
• Explain helm create, helm package, and helm install commands
• What does this replicas: {{ .Values.replicaCount }} mean?
• How does helm templating work?
• What is Jinja?
• How can you see the story of the releases in helm?
• Describe how to perform a go to the previous version in helm

Platform Engineering

• What is Platform Engineering?
• What is the difference between DevOps, SRE and Platform Engineering?
• What is the tooling you use for Platform Engineering?
• Should I go Platform Engineering if I have one product and one team?

See: https://github.com/mbianchidev/platform-engineering-roadmap

OpenShift

• Do you have any experience with OpenShift Container Platform?
• What is OpenShift?

Ansible

• What is the difference between Playbook and Role?
• How do you debug a Playbook?
• How would you use Ansible to automate the deployment of a web application?

AWS

• Define these AWS Services: EC2, S3, Route 53, Lambda, IAM
• What kind of different Load Balancers does AWS offer?
• Define these networking resources in AWS: VPC, ACL, NACL
• What’s the difference between EKS, ECS, and ECR?
• What is CloudFormation and how does it work?

Azure

• How would you deploy a web application to Azure App Service?
• Can you explain the difference between Azure Virtual Machines and Azure Kubernetes Service (AKS), and when you might choose one over the other?
• How do you configure Azure Active Directory for use in a single-sign-on (SSO) scenario?

Software Engineering

Backend

• Explain SOLID principles
• Do you know any design pattern? Pick your favorite one and explain it (e.g. Decorator, Facade, Observer)
• What is a RESTful API?
• What’s the difference between 2xx, 4xx, and 5xx error codes?
• What is a Microservice architecture and how it differs from a monolithic one?
• Explain OOP
• Explain functional programming
• Explain what is a Queue in programming and make some examples of different types of Queues (LIFO, FIFO...)
• How do you handle errors in your code?
• What is a distributed system?
• Have you ever used a message broker? What is it and how does it work?
• What is a cache? What is it used for?
• Why is redis so fast?

Microservices

• Why should I use separate data storage for each microservice?
• What does it meen to keep code at a similar level of maturity?
• What entails to separate build for each microservice?
• Should I assign each microservice multiple responsibility?
• Are containers useful in microservices?
• Stateless microservices seem to be bad. Can I go stateful with microservices?
• Should I Adopt DDD (Domain Driven Design)?
• Orchestrating microservices is not easy. What are the options?

Backend Engineering Scenarios

• What’s canary deployment?
• What if I have two deployments 1.0 (production, stable) and 1.1 (test, maybe stable) and I want to test 1.1 with production traffic, without using the canary deployment technique, what alternatives have I got?
• What if I have a log file that multiple processes write to, how can I make sure that the log file is not corrupted?

Database

• What kind of databases do you know? Pick one and convince me it's the best kind of db ever for my application (e.g. In memory, time series, document, vectorial)
• Explain DB data structures (e.g. B-Tree, Hash Table, LSM tree etc.)
• What is a query execution plan? Can you "explain" it?
• What is a transaction? What's the definition of ACID?

Frontend

• What is responsive design and how is it achieved?
• What is a CSS preprocessor?
• What is a media query in CSS?
• What’s a CDN?
• How can it help to improve a frontend?
• What kind of CDN have you used?
• What’s caching and how does it work?
• What kind of caches have you used?
• How can you test frontend?
• Have you got any experience with Selenium, Cypress, or Storybook.js?

React

• What are the benefits of using a virtual DOM in React?
• What is the difference between state and props in React?
• What’s the difference between a class component and a functional component?
• How routing works in React?
• What is the difference between controlled and uncontrolled components in React?
• What is Redux?

Angular

• What is the difference between ngOnChanges and ngOnInit in Angular?
• What is Angular's change detection mechanism?
• What is an Angular service?
• What is dependency injection in Angular?
• What is Angular routing?
• What is the difference between a component and a directive in Angular?

Frontend Engineering Scenarios

• What are microfrontends?
• What are the benefits of using micro frontends?
• What is a Progressive Web App (PWA)?
• What are the benefits of using PWA?
• What are the key features of a PWA?
• How can you optimize a PWA for performance?
• Client Side Rendering (CSR) vs Server Side Rendering (SSR), explain the concepts
• Can you describe your approach to optimizing the performance and user experience of a large e-commerce website?
• How would you approach building a highly interactive and responsive web application with real-time updates? E.g. Financial App Stock Market data

Behavioral (I don't usually ask these questions)

• Describe a time when you disagreed with a team member. How did you resolve the problem?
• Describe a time when you faced a block at work and how you solved it.
• Tell me about a time when you disagreed with a supervisor.
• What is the most difficult/ challenging situation you’ve ever had to resolve in the workplace?
• Describe a time when you were able to motivate unmotivated team members.
• Tell me about a decision that you’ve regretted and how you overcame it.
• Tell me about a time when you tried something risky and failed.
• Tell me about a time when you were consulted for a problem.
• Explain a time when you took the initiative on a project.
• What’s the best idea you’ve come up with on a team-based project?
• Tell me about a time when you worked well under pressure.
• So, tell me a bit about yourself…
• Why do you want to work here?
• Where do you see yourself in X years? (X = 3, 5, 10)
• What do you do outside of work?
• What are your strengths and weaknesses?
• Why are you leaving your current job? (not for interns/new grad)
• Who is your idol?
• What is your favorite book?
• Why startup|big tech|[insert here kind of company or industry]?
• How do you see [insert here industry] in the next 5 years?
• What would be your perfect job description?

Outro

• Are you happy with our salary offering?
• What benefit would you like to see listed?
• What benefit are you glad we offer?
• What is your notice period?
• When would you be available to start?
• Do you have any questions for me?