US Patent 7840557 Search engine cache control

A search query containing at least one term is received at a search controller from a query server and preferably normalized and hashed into a representation of the search query. The representation of the search query is transmitted towards a cache containing multiple query result entries. Each query result entry contains a list of documents associated with the previously searched search query. The cache is then searched and query result entries for the search query are sent to the search controller from the cache. Subsequently, it is determined whether the query result entries are current versions for the search query. If the query result entries are not the current versions, then current versions of the query result entries are obtained.