This document discusses Redis, an open source in-memory data structure store. It begins with an introduction to Redis and what it is. It then covers the different data structures Redis supports like strings, lists, sets, sorted sets, and hashes. It discusses some powerful features of Redis like transactions, persistence, replication, pipelining, and clustering. It compares Redis to Memcached and shows examples of using Redis in practice with Resque, RestMQ, and for statistics and searching.