I can also recommend checking out rethinkdb. It feels like MongoDB but without many of the downsides. Not saying MongoDB is bad (I've used Mongodb and like it)

I can also recommend checking out rethinkdb. It feels like MongoDB but without many of the downsides. Not saying MongoDB is bad (I've used Mongodb and like it), but much of their API-design is quirky/bad, locking is an issue and mmap feels weird too.