A lot of the caching we're doing is just plain key/value and so it was easier to just increase our usage of Memcached (we were already using Memcached at the ti

A lot of the caching we're doing is just plain key/value and so it was easier to just increase our usage of Memcached (we were already using Memcached at the time). If we need to store more complex structures in memory (e.g. lists) then Redis will be high on the list of choices. Since I wrote this piece, we've been looking in to reworking our notifications and activity feeds so there's a good possibility that we will be looking in to Redis again.