This document summarizes the open source Riak database from Basho Technologies. Riak is a distributed, fault-tolerant key-value database written in Erlang. It provides simple, elegant scalability through a gossip protocol and consistent hashing to distribute data across nodes. Riak aims for ease of operations, resiliency to failures, and easy development through RESTful APIs and client libraries. It is used by both startups and Fortune 100 companies for applications such as session storage, timelines, and full-text search.