Khepri is an interesting alternative to Neo4j for a program I wrote to store tree data a few years ago. Of course, I'd have to try it out with actual data, but

Khepri is an interesting alternative to Neo4j for a program I wrote to store tree data a few years ago. Of course, I'd have to try it out with actual data, but it seems performant in the few minutes I've been fiddling with it.