> However if we are to jump on in JDK world, persistence is not hard. Java have supurb db like H2 with full postgres compliance, that can be embedded in memory.

> However if we are to jump on in JDK world, persistence is not hard. Java have supurb db like H2 with full postgres compliance, that can be embedded in memory. H2 is a cute database, but it doesn't even come close to having "full postgres compliance". Besides, it solves a completely different problem from Permazen or JPA - it's a storage engine, not a storage abstraction layer.