In a content delivery network (CDN a method includes: receiving a request for a CDN service of a particular type, wherein a CDN service of said particular type defines a fixed number of configurable layers of request processing, sequentially from a first layer to a last layer; and processing said request, starting at said first layer, said processing being based on a modifiable runtime environment, said processing continuing conditionally through each of said layers in turn until either said request is terminated by one of said layers or said last layer processes said request. A layer may cause some of the processing of a request to be handled by another service. The CDN service may be selected from: delivery services, collector services, reducer services, rendezvous services, configuration services, and control services.