Postgres works well. Neo4j. Persistence is pretty well solved. So is the in-memory representation! Have you thought about using lazy structures? The graph can

Postgres works well. Neo4j. Persistence is pretty well solved. So is the in-memory representation! Have you thought about using lazy structures? The graph can be conceptually infinite in size but your program only loads the pieces being used as they are needed and offloads old ones that are not.