SenseiDB - Distributed, Realtime, Semi-Structured Database from LinkedIn

Sensei is a distributed data system that was built to support many product initiatives at LinkedIn, including the real-time faceted search in LinkedIn Signal and the news feed and tabs on the Homepage. Sensei is both a search engine and a database. It is designed to query and navigate through documents that consist of unstructured text and well-formed and structured metadata.

It supports Fast realtime updates, Complex query language and REST/JSON api, Hadoop integration and lot more.