Have you noticed? messageagency.com is quite a bit snappier. Pages load before you look up from your keyboard. The browser barely has time to spin before the page is delivered. We haven't performed any formal benchmarking, but the subjective performance has improved dramatically since migrating to Linode and Mercury.

Mercury is a collection of software that combines a reverse proxy, Varnish, a sophisticated caching engine, Memcache, and Pressflow, a performance-tuned Drupal distribution. There are lots of resources to help you get up and running, but the most daunting was migrating our existing site. After biting the bullet, we discovered that upgrading was only slightly more complicated than updating Drupal. Documentation from official sources was scant, but eventually this short post from a random blog proved invaluable. There's also a more verbose version of the documentation available on d.o.