[Meta] ✂️ Cut loading time

[sarahsporck]

We currently have quite long loading times when opening a URL of a single page directly in the web app. Google times the full rendering process usually between 2.5 and 3.5 seconds and classifies this as not fast. We should investigate low hanging fruits and potentially longer term improvements which we can implement. This necessarily requires app and CMS teams to work together.

For further context, there are some initial discussions in Mattermost:

• https://chat.tuerantuer.org/digitalfabrik/pl/i5wu5kfgcpne7bwpkatr6en7cr
• https://chat.tuerantuer.org/digitalfabrik/pl/n3843gcpntneubgf4wdgputhbr

Some basic things we can do:

• Use more parallelization
• Remove unnecessary things (for example trailing slash redirects)
• Reduce amount of transferred data
• Optimize computation in the CMS and app

Tasks

• [x] #2261
• [x] #2234
• [x] #2198
• [x] #2153
• [x] #2152
• [x] #2151
• [x] #2328
• [ ] #2277
• [ ] #2435
• [ ] #2436
• [x] #2498
• [ ] #2499

[steffenkleinle]

@ztefanie do you think any of the still open issues will reduce our page loading times on mobile significantly enough to increase our google search score? 19000 of our URLs are marked as Improvment needed by google because of a LCP longer than 2.5 seconds: https://search.google.com/search-console/core-web-vitals/drilldown?resource_id=https%3A%2F%2Fintegreat.app%2F&item_key=CAMQAhgC

Otherwise I guess we would need to investigate more...

[ztefanie]

@steffenkleinle No they won't.

Biggest improvments will be made by: 1) Minimizing main thread work 2) Speed up JS execution

[steffenkleinle]

@steffenkleinle No they won't.

Biggest improvments will be made by:

1. [Minimizing main thread work](https://developer.chrome.com/docs/lighthouse/performance/mainthread-work-breakdown/?utm_source=lighthouse&utm_medium=lr#how-to-minimize-main-thread-work)

2. [Speed up JS execution](https://developer.chrome.com/docs/lighthouse/performance/bootup-time/?utm_source=lighthouse&utm_medium=lr#how-to-speed-up-javascript-execution)

Thanks, I created to issues:

1. 2498

2. 2499