Optimize Loading Performance

[chfsx]

Describe the bug
Not really a bug, but something we could investigate further: loading times for large series are sometimes very long. A cache (database or APCu) was introduced some time ago, but this has not led to a significant improvement in performance.
I will try to document some of the areas where I see potential for optimisation in the near future.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Events' Sreen of a series with many events

Expected behavior
Best case would be loading times around 500ms

Screenshots

Log

Environment (please complete the following information):

• ILIAS version: any
• PHP version: 8+
• Plugin version: 9/10
• Opencast version 17.x as far as i know
• Browser: any

Additional context

[chfsx]

One initial finding is that loading events from the API takes a lot of time, especially because this has to be done twice:

• once to find out how many events are displayed based on the filters
• once to load the displayed events
  which results in ~35% of the loading time

There is certainly a lot of potential here to improve performance. I will start doing further research here.