RethinkDB is a distributed document-store database that is focused on easy of administration and clustering. RethinkDB also features functionality such as map-reduce, sharding, multi-datacenter functionality, and distributed queries. Though the database is relatively new, it has been funded and is moving quickly to add new features and a Long Term Support release.
One major issue still remains with RethinkDB, however– it’s relatively difficult to secure properly unless you have security group or virtual network functionality from your hosting provider (a la Amazon Web Services Virtual Private Cloud, security groups, etc.). For example, RethinkDB’s web administration interface is completely unsecured when exposed to the public Internet, and the clustering port does not have any authentication mechanisms. Essentially, this means that if you have an exposed installation of RethinkDB, anyone can join your database cluster and run arbitrary queries.