1. A method of prioritizing a refreshing of items provided in response to queries, the items stored in an item cache by a computer having a processor, respective items corresponding to a source item retrieved from a source item host accessible to the computer, and the method comprising: executing on the processor instructions configured to: for respective items: predict a query frequency of queries requesting the item, predict an update frequency of the source item by the source item host, and compute a refresh utility of the item based on the query frequency and the update frequency; and prioritize refreshing a first item of the item cache having a first computed refresh utility over refreshing a second item of the item cache having a lower computed refresh utility than the first computed refresh utility of the first item.