Redis is described as '(REmote DIctionary Server) is an open-source, networked, in-memory, key-value data store with optional durability. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets' and is a very popular app in the development category. There are more than 25 alternatives to Redis for a variety of platforms, including Linux, Windows, Mac, Online / Web-based and BSD. The best alternative is MongoDB, which is free. Other great apps like Redis are Apache Cassandra, CouchDB, RethinkDB and memcached.
Apache Cassandra has become the leading NoSQL platform driving many of today's modern business applications by offering continuous availability, high scalability and performance, strong security, and operational simplicity while lowering the overall cost of ownership.
Most users think Apache Cassandra is a great alternative to Redis.
Apache CouchDB is a distributed, fault-tolerant and schema-free document-oriented database accessible via a RESTful HTTP / JSON API. It includes incremental map / reduce mechanics for queries and keeps data safe with an append-only datastore.
Cockroach is a distributed key/value datastore which supports ACID transactional semantics and versioned values as first-class features. The primary design goal is global consistency and survivability, hence the name.