OrientDB is a NoSQL graph database which also includes a document layer (like MongoDB): it gained a lot of attention, enough to push big companies like Sky and UltraDNS to use it in production: it's written in Java and it's amazingly fast, since it can store up to 150,000 records per second on common hardware; moreover, thanks to being a graphdb, it can manage relationship so fast that, compared to traditional DBs, can be 1000% faster than them.