Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for managing system resources. In one aspect, a system monitors the number of items, and deallocates system resources for the least-important items when the number of items exceeds a predefined capacity. The importance of each item is determined, for example, based on the item's subscription count such that system resources are utilized for the benefit of the greatest number of users or to improve the quality of service.