Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for aggregating requests for resources. In one aspect, a method includes receiving a set of requests for computing resources. Each request specifies one or more computing resources and, for each of the one or more computing resources, a quantity of the computing resource requested. A quantity-based provider condition that a request must meet for inclusion in an allocation process is identified. Each received request that fails to meet the quantity-based provider condition is included in a proper subset. Requests in the proper subset of requests are grouped into one or more groups based at least on the quantity of the one or more resources specified by each request of the proper subset and the quantity-based provider condition. A respective combined request is generated for each group of requests.