Today the FoundationDB Document Layer was released! From the announcement:
The FoundationDB Document Layer provides the ease-of-use of a document database in the form of the familiar MongoDB® API. The Document Layer is a stateless server, backed by the scalable and transactional features of FoundationDB.
To learn more, see the project documentation. The Document Layer project is hosted on GitHub and binary downloads are available for macOS and Linux. We’ve also added a new section to the forums for the Document Layer.