An application combines on-site and cloud-based calculations. The application selects a cloud computing broker from a list sorted by load. The broker receives computation requests from the application, sends corresponding load-balanced requests to local application service hosts and cloud proxies, receives responses, and sends the responses to the application without identifying the response source as local versus non-local. Each proxy has a logical-physical mapping of cloud-resident worker nodes. A scheduler receives session requests from applications, allocates local and cloud computing resources to a session, and tracks resource usage by session. An application previously run only on-premises can be executed partially on cloud worker nodes without modification. The proxy re-routes unfulfilled requests from a failed worker, undetected by the broker. If all workers assigned to that proxy fail, then the broker reassigns unfulfilled requests to another proxy, undetected by the application.