And the expansion on this is - DB_File (or its big brother BerkeleyDB has a tied hash database (or you can eschew the tying if you like and just it directly. Somewhat like Cache::Cache except different) which is sorted by key. You're pushing the sorting off to the SleepyCat db in C and during the store operation instead of retrieval. Its almost certain you'd want to tweak some of the cache or page settings though.