Availability : Open Source NoSQL Database.
Written in : Erlang.
Products : Riak KV and Riak TS.
It is a key-value based NoSQL database that can be used to store user session related data.
Riak KV is one of the distributed NoSQL databases.
Riak TS is built on the same core foundation as Riak KV and is highly optimized for IoT and time series data.
It also integrates with Riak S2 to optimize large object storage.
Also it integrates with other data services including Apache Spark, Redis Caching, Apache Solr, and Apache Mesos.