RethinkDB - Distributed JSON database
RethinkDB is built to store JSON documents, and scale to multiple machines with very little effort. It has a pleasant query language that supports really useful queries like table joins and group by, and is easy to setup and learn. It supports JSON data model, Distributed joins, subqueries, aggregation, atomic updates, Hadoop-style map/reduce.
It is scalable, supports sharding and replication to multiple nodes. It takes care of machine failures and network interrupts.