ConsistentMap's key equality is based on serialized byte.
(1) By caching Key -> String representation,
Cache will use Key's Object#equals for look up,
which can possibly have different equality than byte equality,
leading to wrong String to be used as a key in backend Database.
(2) Similar issues with keySet(), entrySet()
Set based on reference equality needs to be used to avoid
deduplication based on Object#equals