To scale to millions of Internet users with good performance, content delivery networks (CDNs) must balance requests between content servers while assigning clients to nearby servers. In this paper, we describe a new CDN design that associates synthetic load-aware coordinates with clients and content servers and uses them to direct content requests to cached content. This approach helps achieve good performance when request workloads and resource availability in the CDN are dynamic. A deployment and evaluation of our system on PlanetLab demonstrates how it achieves low request times with high cache hit ratios when compared to other CDN approaches.