Elasticsearch is an open source NoSQL database that can downloaded here.

- Elasticsearch is a search engine that was designed to work on the cloud.

- It uses a distributed search engine that isn't based on a single central server.

- Elasticsearch allows for running searches in close to realtime.

- It supports multiple search indexes.

- Indexes are sharded so that the load can be spread among multiple database servers.

- Each shard is a Lucene index.

- It's a schema free database - it uses documents rather than tables. You don't need to begin with a structure of rows and columns.

Relativity Data Grid uses Elasticsearch with the Audit application, which runs reports on user activity.