I use this database in my apps to solve exactly this problem (US only): http://federalgovernmentzipcodes.us/ http://federalgovernmentzipcodes.us/ No idea who r

I use this database in my apps to solve exactly this problem (US only): http://federalgovernmentzipcodes.us/ http://federalgovernmentzipcodes.us/ No idea who runs it but its updated regularly and has never caused issue (so far). It includes both the USPS preferred city and all possible cities so you can either default to preferred or provide at least auto complete. Its also has all the military addresses and as well as lat/long, which is a bonus. I can see the ziptastic concept being interesting if it was fully international but for just the US it takes about 15 minutes to download the linked csv, toss it in a DB table, and write the 3 queries you need. I don't understand the need for a service to handle such a simple task.