To add my 2 cents here: I've been using both memcached and redis in various projects and for me they serve slightly different purposes. For plain old caching I

To add my 2 cents here: I've been using both memcached and redis in various projects and for me they serve slightly different purposes. For plain old caching I haven't (yet) had a need to use redis, which is younger and by nature more complex. RAM is so cheap nowadays, we just tend to stuff two memcached machines with 64G, which goes a ridiculously long way. On the other hand, as antirez pointed out, redis shines when you need "a little more than caching". We have rolled a few custom queueing solutions on top of redis (similar to resque) and working with lists and the SUBSTR operation is an extremely pleasant experience. Redis seems to be the optimal "roll-your-own-queue" toolkit at this point. We had some strong delivery- and persistence-guarantee requirements in our project but those were not a problem to meet with a simple WAL on the clients and a redis-pair. So far our solution wins over the previous rabbitmq setup big time in all areas (performance, reliability, complexity, transparency). It could have been done with memcached, but less efficiently due to the lack of the aforementioned list-operations.