Moodle seems to be extremely slow when it comes to processing access restriction for modules with course completion rules.

Steps to reproduce the problem:

• Create a course
• Add a module to the course (e.g. an assignment)
• Now start adding another module to the course (e.g. a quiz)
  • Under the "Restrict access" tab you need to click "Add restriction" and click the "Activity completion" button in the popup. Afterwards select your first module (the assignment) and save the module with the default restriction settings.
• Create a lot of modules with these types of restrictions. Some of the modules should also rely on the completion of multiple other modules.

When you got hundreds of these restrictions the course will become extremely slow. The course will no longer take seconds to load but minutes.