12. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: obtaining first profile data for a first user that is associated with a computing device; obtaining second profile data for second users that submitted search queries, the second users being different from the first user; determining, based on the first profile data and the second profile data, similarity scores that are each indicative of a degree of similarity between the first user and at least one of the second users; selecting a proper subset of the search queries based on the similarity scores; generating an update for an autocomplete cache of the computing device associated with the first user using the selected subset of the search queries; and providing the update to the computing device associated with the first user.
12. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: obtaining first profile data for a first user that is associated with a computing device; obtaining second profile data for second users that submitted search queries, the second users being different from the first user; determining, based on the first profile data and the second profile data, similarity scores that are each indicative of a degree of similarity between the first user and at least one of the second users; selecting a proper subset of the search queries based on the similarity scores; generating an update for an autocomplete cache of the computing device associated with the first user using the selected subset of the search queries; and providing the update to the computing device associated with the first user. 22. The system of claim 12 , wherein: obtaining the first profile data for the first user comprises obtaining a first search query history for the first user; obtaining the second profile data for the second users comprises obtaining second search query histories for the second users; and determining the similarity scores comprises determining the similarity scores based on commonalities between the first search query history and the respective second search query histories.