InMemmoryStorage optimization

[Sytten]

We use synchronize in the InMemoryStorage, but we already use a ConcurrentHashMap. If we modify slightly the way we override the keys, it would possible to remove them.

Also, the ConcurrentHashMap uses the default values at creation (meaning its optimized for 16 threads), we should adjust that for our own needs (I suggest 4 threads to be more realist). The gain in performance should be significant.

[Sytten]

Hey guys that should be an easy fix that would increase performances.