memcached is about a bazillion times faster than redis at doing the simple KV cache job. it’s got threads. it’s highly optimized to do its one job super well, where redis is more a arbitrary shared Python heap kinda thing with all the data structures and single thread and whatnot.
at notion we use redis for a lot of things, but actual caching we leave to memcached
Can confirm it's not that much faster at k/v. 300 vs 350 microseconds per read on average. The single thread thing doesn't matter much since it's not cpu bound, it's reactive I/O
Threads are not free - they allow to use more CPU cores but if you load is not too high than with a single thread memcached uses less CPU than with multiple.