Pinot

Pinot is a realtime distributed OLAP datastore, which is used at LinkedIn to deliver scalable real time analytics with low latency. It can ingest data from offline data sources (such as Hadoop and flat files) as well as online sources (such as Apache Kafka). Pinot is designed to scale horizontally. Pinot leverages Apache Helix for cluster management.

Github: https://github.com/linkedin/pinot

Architecture : https://github.com/linkedin/pinot/wiki/Architecture

http://engineering.linkedin.com/analytics/real-time-analytics-massive-scale-pinot