After reading about MySpace dealt with their scaling up to support millions of users, I decided it was a good idea to review my application's architechture, and identify what areas could scale independently, and what areas need optimization.
I first outlined the application that generates ArtistServer into seven parts - there's opportunity for optimization everywhere, so by looking at the applicaiton in different ways, I feel you can better identify those optimization points.
Application Zones - the site divided into zones of functionalitySub-Applications - areas of the application which