Redis is an open source and distributed in-memory caching server. Redis is an abbreviation of REmote DIrectory Server. It is one of the most popular in-memory key-value data stores. Redis provides such functionalities as caching, pub/sub, session management, and leaderboards.
Amazon provides a fully managed service for Redis and provides a customer managed Redis server on an EC2 instance. Using AWS ElastiCache for Redis, users will be free from the burden of managing administrative tasks such as installing, configuring, software patching, version upgrading, and so on. Redis also provides support for replication, where we can have a master/slave server and data will be asynchronously replicated on multiple slave servers. Using the replication feature, Redis can handle failover of the primary server by making the slave server the primary server.