Your plan doesn't make any sense. As opposed to single big calculations, which needs to be broken in to small chunks for parallel processing, Moodle is a web application. It already gets its work in form of a large number of browser requests. Means, there is no need to break the job in to small chunks as in big single calculations. The threading is handled by the web server at the operating system level. See http://dubbo.apache.org/en-us/docs/user/demos/thread-model.html for the Apache thread model.
If your question is how to build a Moodle server for heavy loads, there is a dedicated forum, the Hardware and performance forum, for that. Have a careful look at its documentation https://docs.moodle.org/en/Performance and https://docs.moodle.org/en/Performance_FAQ. There is also a knowledge base in form of recent discussions.