Interaction between a client and a service in which the service responds to requests from the client. In addition to responding to specific client requests, the service also anticipates or speculates about what the client may request in the future. Rather than await the client request (that may or may not ultimately be made), the service provides the unrequested anticipatory data to the client in the same data stream as the response data that actual responds to the specific client requests. The client may then use the anticipatory data to fully or partially respond to future requests from the client, if the client does make the request anticipated by the service. Thus, in some cases, latency may be reduced when responding to requests in which anticipatory data has already been provided. The service may give priority to the actual requested data, and gives secondary priority to the anticipatory data.