HBase

HBase is the Hadoop database. It is an open-source, distributed, versioned, column-oriented store that provides linear and modular scalability.   Apache HBase began as a project out of a need to process massive amounts of data for the purposes of natural language search.  It aimed at hosting very large tables atop commodity hardware. Thus, it is built upon distributed filesystems so that the underlying file storage can be spread out among an array of independent machines. It is mostly used where random, real-time read/write access to the Big Data is required.

Other than strictly consistent reads and writes, HBase also provides automatic and configurable sharding of tables and an easy to use Java API for client access amongst many other features.