The linked Open edX course is pretty incomplete.
The section on the Open edX stack points the reader to an additional course
"For further reading, please see the Open edX architecture course if there is time left in your onboarding budget." That course however seems to be under construction, there is very little content in it.
https://learning.edx.org/course/course-v1:edX+101+arch2018/home
Edited by Jani Monoses