I'd probably reach for RethinkDB before Postgres or others simply for the better administrative experience. Especially for small teams or start-ups that don't have a dedicated DBA role.
For anyone curious, the databases I would most likely reach for, depending on the situation would be RethinkDB, ElasticSearch and Cassandra. I really do like MongoDB a lot as well, but RethinkDB offers the features with far less friction, though the query interface takes a bit of getting used to.
That said, I also like more traditional RDBMS options as well. I REALLY like what PostreSQL offers, but have no desire to administer such a beast, failover isn't really baked in, and the best options are only commercially available, at a significant cost. There are also hosted options for AWS and Azure for various SQL RDBMS. That said, I find being able to have data structure hierarchies in collections tends to be a better fit for MANY data needs.
Congratulations to Slava and everyone else at RethinkDB.