Redis, standing for REmote DIctionary Server is a NoSQL databases Server. Written in ANSI C by Salvatore Sanfilippo in early 2009 and quickly become the most popular key-value store.
Similar to Memcache, Redis has in-memory key/value store but with extra features like: persistence, more value types(lists, sets, sorted sets, hash table..), open source with large community and of course, it’s FREE !
Get/Set/Incr strings or numbers
Redis Lists are simply lists of strings, sorted by insertion order. It is possible to add elements to a Redis List pushing new elements on the head (on the left) or on the tail (on the right) of the list.
Simple Redis list
Redis Sets are an unordered collection of Strings. It is possible to add, remove, and test for existence of members Set
Redis Sorted Sets are, similarly to Redis Sets, non repeating collections of Strings. The difference is that every member of a Sorted Set is associated with score, that is used in order to take the sorted set ordered, from the smallest to the greatest score. While members are unique, scores may be repeated
Redis Hashes are maps between string fields and string values, so they are the perfect data type to represent objects