1. A method comprising: determining an estimated number of items that match a first structured query by a computing device, wherein the first structured query comprises one or more attributes values and each attribute value is associated with an attribute; determining if the estimated number of items is below a threshold number of items by the computing device; and if the estimated number of items is below the threshold number of items: determining a plurality of candidate structured queries from the first structured query by the computing device, wherein the number of candidate structured queries in the plurality of candidate structured queries is proportional to a maximum time; for each candidate structured query of the plurality of candidate structured queries, estimating a number of items that match the candidate structured query by the computing device; determining the candidate structured query with the highest estimated number of items as a second structured query by the computing device; determining a plurality of items that match the second structured query by the computing device; and providing indicators of each of the determined plurality of items by the computing device through a network.