A content delivery network, or CDN, is a system of servers spread around the world, serving files from the nearest physical location. Instead of waiting for a file to find its way from a server farm in Silicon Valley 8,000 kilometres away, I can receive it from London, Dublin, or Paris, cutting down the time I wait. The big names — Google, Yahoo, Amazon, et al — use CDNs for their sites, but they’ve always been far too expensive for us mere mortals. Until now. There’s a service out there ready for you to use as your very own CDN. You have the company’s blessing, you won’t need to write a line of code, and — best of all — it’s free. The name? Google App Engine. In this article you’ll find out how to set up a CDN on Google App Engine. You’ll get the development software running on your own computer, tell App Engine what files to serve, upload them to a web site, and give everyone round the world access to them.