Initially released in 2009, Redis is intended for applications where performance and flexibility are more important than persistence and absolute data integrity. It is an open-source key/value store written in C. Keys can contain strings, hashes, lists, sets, and stored sets. Redis works in RAM for speed, occasionally dumping to disk. Because actions are performed in memory, they are done faster. Operations include appending to a string, incrementing a hash value, pushing to a list, set computations, and more. Redis is also designed so that master-slave replication is easy to set up.