US Patent 11119826 Serverless call distribution to implement spillover while avoiding cold starts

Systems and methods are described for reducing cold starts code within a serverless code execution system by providing a set of environments reserved for the code. A frontend distribute calls for execution among a set of manager devices that manage environments in the system, distributed in a manner that groups calls together and attempts to distribute calls of the same group to a stable subset of the manager devices. In the case that a user reduces or eliminates the number of environments reserved for the code, a frontend continues to distribute calls for execution of the code to those environments while they continue to be used. This reduces cold starts that might otherwise occur during reduction or elimination of reserved environments.