RethinkDB is a document-oriented database similar to MongoDB but aims to overcome scalability and practical limitation of the latter.   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.
# yaourt -S rethinkdb
Now you can start rethinkdb from command-line:
Or instead you can run it as systemd service. Enable default rethinkdb instance as
# systemctl enable rethinkdb@default
and start it:
# systemctl start rethinkdb@default
Admin UI will be available at 8080 port.
RethinkDB has multi-instance support, which means you can run several independent database instances at the same machine. Systemd service also supports multi-instance configuration.
To create a new RethinkDB instance create its configuration file:
# cd /etc/rethinkdb # cp default.conf.sample instances.d/<NAME>.conf
where <NAME> is the name of you configuration that you'll going to use later. Change configuration options in the new config file. Then start the service:
# systectl enable rethinkdb@<NAME> # systectl start rethinkdb@<NAME>
'default' instance is created at installation time for your convinence. Its data is stored in /var/lib/erethinkdb/default