This is a just a place-holder/note.
On my TODO list to look up a handful of different key-value stores. There are a few new contenders in addition to a couple of old favorites:
I am especially interested in looking into ehcache as well as riak.
Also, memcached (and couchbase) made this list because we may need to re-evaluate how we are using redis. redis has a handful of good features, like handling pub/sub, but we use none of it. We are strictly looking only for a key-value store, eg ObjectManager.