Comment by c0balt

Redis has a few features outside of k/v, like a good pub-sub implementation, that make it very useful in addition to a good DX and mature libraries.

Memcache on the other habd is just solid and mature. It also has some inertia as being a solid k/v cache. For example: NextCloud supports afaik both Redis and Memcache as caching engines but doesn't have FDB support.