At Dgraph, we're building the most advanced graph database in the world. It does distributed transactions, low-latency arbitrary depth joins, traversals, provides synchronous replication and horizontal scalability — with a simple GraphQL-like API.
Dgraph started around end-August, picked up steam in mid-October, and v0.1 was released in early-December, 2015. From one, the contributors grew to 46, with the project amassing over 4000 Github stars over the past two years.
Amazon just announced their new graph database service, called Amazon Neptune. As per a TechCrunch article,
Amazon Neptune has been optimized to handle billions of relationships and run queries within milliseconds.