Systems and methods are provided for efficiently configuring an execution environment for an on-demand code execution system to handle a single request (or session) for a single user. Once the session or request is complete, the execution environment is reset, such as by having the hardware processor state, memory, and storage reset. In particular, prior to the execution of code, state of the execution environment of the host computing device is retrieved, such as hardware processor(s), memory, and/or storage state. Moreover, during execution of the code instructions, intermediate state can be gathered. Following the execution of the code, the execution environment is reset based on the saved state related to the hardware processor(s), memory, and/or storage. A subsequent code execution securely occurs in the execution environment and the execution environment is reset again, and so forth.