The described technology is directed towards returning expanded data, beyond the data that was specifically requested, to a client, in order to reduce or eliminate likely subsequent requests for more data. Client requests for data items are processed by expansion rule logic to find an expansion rule set (e.g., file) corresponding to the identified data item. The rule set is used to expand requests for certain data items into expanded requests that return more data items than those requested. Client devices receive, cache and (often) use the cached expanded data items, which thereby reduces the overall number of requests to the data service. Expansion rules may be based upon observations (e.g., machine learned and/or manual) of request patterns, so as to reasonably predict which data item or items clients will likely next need, and return those as expanded data items in anticipation of their need.