A metadata query is received in as storage system from a client node that asks one or more questions regarding a set of metadata in a metadata store. The metadata query is executed on at least one metadata summary structure. Each metadata summary structure summarizes a metadata stream of metadata access during a period of time, and different metadata summary structures from different periods of time are periodically merged together so that the metadata query is conducted on a merged metadata summary structure. An answer is returned from the query executed on the merged metadata summary structure.