1. A system for storing and retrieving objects of a first type comprising: a plurality of caches, wherein each entry in each cache comprises a key and an object; wherein the plurality of caches includes a plurality of (n&plus;1)th-level caches, wherein each object in each entry in the (n&plus;1)th-level cache comprises an object of the first type; and wherein the plurality of caches further includes an nth-level cache, wherein each object in each entry in the nth-level cache comprises an identifier of a corresponding (n&plus;1)th-level cache.