Java programs tend to use the memory they're given to provide the best performance in the server environments so it's not conservative in terms of memory allocation. While it does use more memory in a given time, it doesn't necessarily mean that it relies on all the allocated memory. That's one of the reasons why benchmarking is so hard..

Exactly, you are right.

The difference comes from several things, JVM being the first and obvious one. It takes as much memory as whole Memgraph + small dataset in this case. Second is the overallocation that JVM/Neo4j is doing, taking a bit more memory to have future space to grow. The third one comes to the implementations of storage and Neo4j cache implementation, not sure what Neo4j does on that side and how impactful it is. We use a skip list.