US Patent 10048974 Message-based computation request scheduling

A system for routing requests to execute user code based on how frequently the user code is executed is provided. The system may be configured to receive a request to execute user code on a virtual compute system, where the virtual compute system comprises multiple fleets of virtual machine instances. The system may be further configured to determine whether the user code associated with the request satisfies one or more usage criteria, and based on the determination, route the request to the appropriate fleet of virtual machine instances.