``CachingClusteredClient`` registers a callback when a segment gets de-registered which removes the namespace containing all the keys.

Probably for this case we can rely on cache eviction instead as namespace in CachingClusteredClient is segmentIdentifier but in this case this will be a list of segments and its difficult to check all the keys containing particular segment. 
And since we are creating cache key with list of segments everytime, if one of the segments is missing, this will give us a unique key.

Bt the problem with cache is its LRU, it might that keys are left for all time.