1. A system comprising: a data processing apparatus that includes a computer-readable storage medium storing executable instructions that cause the data processing apparatus to: obtain a description of one or more computing resource requirements for execution of an application associated with a publicly available service; and opportunistically obtain access to computing resources from a computing entity that includes at least one private computing device that is external to, and separate from, the publicly available service, by intelligently matching the one or more computing resource requirements to available computing resources of the computing entity that includes the at least one private computing device with private computing resources that are temporarily available from a private computing device source, the intelligently matching performed using a performance optimization analysis.