Redis is an open source, in-memory data structure store, used as database, cache and message broker. It also provides high performance and low latency, simplicity while developing complex functionality and compatibility with a wide variety of systems and languages.
It is blazingly fast and is written in C and is completely in-memory and is optimized to handle millions of operations in a second with less than 1 ms latency in a single server. It also gives in pre-built data structures for database operations which include: Lists, sets, sorted sets, hashes, hyperloglogs, bitmaps and geospatial indexes. It has client libraries in almost every language and active developer community and contributors. Best cases to use Redis would include Real-time analytics, High-speed transactions, High-speed data ingest, messaging queues, session storage, in-app social functionality, application job management, geo search and caching. Redis is also rated as the fastest growing database since 2013, #1 NoSQL datastore and the fastest database. Also, the Twitter timeline is based on Redis.