Redis is another NoSQL database like Mongodb. As the site describes, it is a “key-value cache and store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets, sorted sets, bitmaps and hyperloglogs.”

Redis is designed for all in-memory work and presents a nice set of data structures, much like you’d find in a modern scripting language: scalars, lists, hashes, etc.

While MongoDB is about dealing with large amounts of data represented as documents. It comes with all the necessary plumbing to handle sharding across multiple nodes, replication with automatic failover (replica sets), and a rich high-level query language.

A developer in Craigslist said that they “use MongoDB for data that will exist forever and Redis for transient data that lives a month or less.”

Here is a post depicted the note of Sina Weibo using Redis as data storage.