Redis
Redis is a project like Memcached in that it's an in-memory key/value store. See https://redis.io/topics/introduction for an introduction.
mw:Redis gives details about using it with MediaWiki. The use cases for Redis are a bit different from Memcached (because they are similar, not identical). In particular, Session storage and Job queue management are mentioned as use cases. The consensus on Stack Overflow is that Redis is better [1].
Redis can be found in Wikimedia Operations and throughout MW Core
Docs are at https://redis.io/documentation
References
- ↑ Great discussion comparing Redis to Memcached: https://stackoverflow.com/questions/10558465/memcached-vs-redis