1. A system comprising: computer-executable instructions configured to: receive a first instance of a query at a first time, obtain a query result of the query, the query result including multiple result entries of documents, wherein the multiple result entries are obtained from multiple index servers, cache the query result, receive a second instance of the query at a second time that is subsequent to the first time, after the second instance of the query is received, update the query result with an individual updated result entry obtained from an individual index server without updating at least one other result entry of the query result that was obtained from a different individual index server prior to the second time; and a processor configured to execute the computer-executable instructions, wherein the individual updated result entry used to update the query result identifies one or more changed documents that were identified as being changed after the first time.
3. The system of claim 1 , wherein the computer-executable instructions are configured to: request recomputation of the query in at least some of the multiple index servers based on server information received from the multiple index servers.