The Products.mcdutils product supplies a replacement for the ZODB-based session data container supplied by the Transience product, shipped with the Zope core prior to Zope 4 and available as a separate package after that. Rather than using a ZODB storage as the backing store for session data, as Transience does, Products.mcdutils stores session data in a cluster of one or more memcached servers.
This approach is a bit of a cheat, as it uses the daemons as primary stores, rather than as caches for results of an expensive query. Nevertheless, the semantics are not a bad match for typical session usage.