Redis vs Memcached

One major difference is that Memcache has an upper memory limit at all times, while Redis does not by default (but can be configured to). If you would always like to store a key/value for certain amount of time (and never evict it because of low memory) you want to go with Redis. Of course, you also risk the issue of running out of memory

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Memcached is good at being a simple key/value store and is good at doing key => STRING. This makes it really good for session storage.

Redis is good at doing key => SOME_OBJECT.

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