An Internet infrastructure delivery platform operated by a provider enables HTTP-based service to identified third parties at large scale. The platform provides this service to one or more cloud providers. The approach enables the CDN platform provider (the first party) to service third party traffic on behalf of the cloud provider (the second party). In operation, an edge server handling mechanism leverages DNS to determine if a request with an unknown host header should be serviced. Before serving a response, and assuming the host header includes an unrecognized name, the edge server resolves the host header and obtains an intermediate response, typically a list of aliases (e.g., DNS CNAMEs). The edge server checks the returned CNAME list to determine how to respond to the original request. Using just a single edge configuration, the CDN service provider can support instant provisioning of a cloud provider's identified third party traffic.