HyperDex

HyperDex is a modern NoSQL store offering ACID transactions, schema-less documents, a rich API, strong consistency guarantees and fault tolerance.  It keeps all data sharded across a collection of machines, and uses novel techniques to coordinate the data on this cluster to provide its features.

HyperDex is fast - outperforming MongoDB and Cassandra on industry-standard benchmarks by a factor of 2X or more. It automatically replicates data to tolerate a configurable number of failures and automatically redistributes data to make use of new resources as you add more nodes to your cluster.

See: http://bit.ly/1n3q9Xy