The average web page size is greater than 2MB, and increasing. And great swathes of that are images. Serving the right size of image can vastly improve the experience for your users. But while we're arguing about whether Rails is slow or not we're chucking vast images at peoples phones over EDGE connections.
Serving images should be a 'solved' problem, just like it is for 'hosting' or authentication. However lots of solutions make poor default suggestions. What can we do for our users with 100 lines of code, Sinatra, a single gem and a CDN?