Unless their business revolves around serving arbitrarily sized versions of user images, they're probably doing that wrong too. The "solved" way to deal with t

Unless their business revolves around serving arbitrarily sized versions of user images, they're probably doing that wrong too. The "solved" way to deal with this is to generate all the sizes your app will need and store them on the CDN. Resizing images is pretty much the most expensive thing you do in a run-of-the-mill web app. Best to do it once and be done with it, especially now that cloud storage is so cheap. And speaking of cheap, Cloudfront is as close to free as S3 itself. It will roughly double your S3 bill, leaving you paying a grand total of $8.04 per month for your image hosting on a ~1,000,000 unique/month site. Remember the 90's when that would run you $400/month? It's so cheap that it's not worth calculating. Just flip on Cloudfront, configure your CNAME and get on with your life.