Currently there is no synchronisation around script compilation. This means that if a particularly heavy script is in use, many threads may end up compiling the same script.
It would seem like a good idea to have some some sort of synchronisation to prevent ever getting to this stage.
In addition, there will be cases where users will repeatedly submit broken scripts to the server. In this case it is useful to log the error the first time the script compilation is attempted and then cache the error for subsequent runs.
Finally I have found some scripts take in excess of 30 seconds to compile. To aid performance debugging the script compilation times should be included in the logs.