I used Memcached because it seemed more common in the PHP world, probably because it's been around for longer. I thought it would be available on more hosts (though I don't know if that's 100% accurate as I couldn't find hard stats).
Memcached is also simpler and apparently more memory-efficient for our use case in Q2A.
My intention was to add a new plugin type to allow users to use a different type of caching, but I never got around to it. You could do it with a core hack in qa-src/Storage/CacheFactory.php if you wanted to use Redis. |