How about EdgeDB? Never used it, but I found it when looking for a similar thing to you after reading this article. It's built on top of PostreSQL, uses it as a

How about EdgeDB? Never used it, but I found it when looking for a similar thing to you after reading this article. It's built on top of PostreSQL, uses it as a storage engine and provides a NoSQL interface to it. It calls itself a "graph-relational database."