Reconfiguration of execution environment pools for serverless functions

Abstract

Systems and methods are described for reducing performance variance of code executions on a serverless code execution system. A serverless code execution system can operate to obtain requests to invoke code and handle such requests by generating an execution environment for the code on a host computing device and executing the code within the environment. In some cases, an execution environment is poorly placed, resulting in underperformance of code executions on that environment and variance in overall performance of the code executions. The present disclosure enables a serverless code execution system to identify underperforming execution environments and to replace such environments with new environments, reducing variation in performance across execution of the code. New environments may be placed on host computing devices asynchronously, using a placement algorithm that includes additional processing relative to an algorithm that operates synchronously to code invocation.