Flexible utilization of capacity to provide computing services mediated by a service broker. The service broker receives a request from a first party for assistance with a service workload as well as an indication from a second party of a willingness to provide service. The service broker matches the parties with each other based at least in part on the capacity of the second party to service the service workload of the first party, manages offloading of the service workload from first party to the second party, and manages billing of a workload provider (such as the first party or the first party's customer) for the offloading engagement.