Distributed processing framework file system fast on-demand storage listing

A system and method for improving the speed of generating a list of previously-uncounted items stored with a computing resource service provider. The system and method involve obtaining a set of keys from a data store, wherein each key of the set of keys corresponds to an item in a group of items, wherein a quantity of items in the group is uncounted. The system and method further includes generating a first sub-listing of keys based at least in part on a first key range of the set of keys by executing a first thread, generating a second sub-listing of keys based at least in part on a second key range of the set of keys by executing a second thread, combining the first sub-listing of keys with the second sub-listing of keys to produce a list of keys, and providing the list of keys.