UPCZilla is a search engine for UPCs (universal product codes), based on the Storeminator (https://www.programmableweb.com/mashup/storeminator) mashup code. It leverages the web services of Amazon, eBay and Commission Junction to search for likely matches for UPCs and then aggregates the resulting data, displaying it in the form of a price comparison listing, lowest price first.
The engine runs as a Wordpress plugin for ease of deployment and employs multiple layers of caching (database and flat-file HTML) to maximize site speed. However, most page refreshes will require cached data to be refetched from one or more web service - maximum cache time is between one hour and 12 hours, due to restrictions on caching imposed by web service providers.
Still, the results are very consistent, only limited by the accuracy of UPC data provided by third parties - at an estimate, less than 1% of UPC searches have products with wrongly-allocated UPCs.