With all Realm Objects, Results, Lists and Queries being frozen, it means there is a higher chance of us "leaking" versions in high concurrency scenarios. It isn't a leak as such, but releasing older versions would depend on the GC.

In order to prevent the file size of the Realm to grow too much, it might be beneficial to add optional close() methods to all classes holding on to native resources.

That isn't ideal and would be annoying clutter in the API. So we should evaluate whether this is really needed.