RethinkDB looks promising

RethinkDB is out – an open-source distributed 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.

An open-source distributed database with an intuitive query language, parallelized queries, and much more! It’s called RethinkDB and you can fork it on GitHub. What’s not to like?