Embodiments described herein involve generating and modifying a sub-index of a media index. An example method may involve receiving requests to play back media items in a media index, tracking the requests to play back the media items in the media index, determining a set of media items from among the media items in the media index based on the tracked requests to play back media items in the media index, and indexing the determined set of media items into a sub-index. The set of media items have been played at least a pre-determined threshold number of times within a pre-determined threshold period of time. The media items in the sub-index are a subset of the media items in the main index.