33. A computer-implemented method for executing search requests, the method comprising: receiving from a user device a search request for a travel reservation, the search request including at least one first constraint to be met by results returned by a search; constructing a first query and a second query for the travel reservation based on the search request, the first query constructed based on the at least one first constraint and at least one additional constraint not included in the search request such that the first query returns a subset of results that would be obtained by a query based on the search request without the at least one additional constraint, and the second query constructed based on at least one constraint not included in the first query; wherein the select at least one additional constraint is performed based on an estimated execution time of the first query with the at least one additional constraint; executing the first query to obtain first phase query results and the second query to obtain second phase query results, wherein the first phase query results and the second phase query results are non-intersecting; transmitting to the user device for presentation, the first phase query results; and transmitting to the user device for presentation, a summary indicating that the second phase query results are available for presentation.
35. The method of claim 33 , wherein executing the first query comprises transmitting the first query to a plurality of information sources to receive search results from the plurality of information sources.