All SonicOS API that modify configuration (POST, PUT, DELETE) do not take effect immediately. Rather, configuration is staged and is not pushed to run-time config or saved to flash/permanent storage until API clients explicitly execute a POST request to /api/sonicos/config/pending. This is the same behavior as SonicOS CLI and equivalent to invoking the commit command from the top-level config mode.
Pending configuration can be canceled (deleted) at any time by executing a DELETE request to /api/sonicos/config/pending. It should be noted that any/all pending configuration is canceled (deleted) upon client session termination, whether due to idle-timeout or explicit logout. In this case, all unsaved changes are lost so it is the client's responsibility to either commit pending configuration after each POST/PUT/DELETE API call or maintain pending changes on the client side to be restored in a later session.