Spike: Investigate ways to improve performance on pipelines page of GitLab project

Problem to Solve

We attempted to solve performance problems on the pipelines page, with the fixes made in 13.12:

• #324003 (closed)
• #329798 (closed)

However we're still seeing slow load times on the page, per #329798 (comment 575428501) and #207994 (comment 300073966)

Projects::PipelinesController#Index is still being requested a lot. This spike is intended to look at ways we can bring the counts down and to propose ways to we can address performance problems on the Pipelines page as a whole.

Current Ideas

Our next step will be to implement #207994 (closed) and then come back to this issue for further investigation about possible fixes.

Update: We implemented #207994 (closed) and we still need more improvements

Further options

• Lighten the workload of the Pipeline Preloader: #331187 (comment 1903582195)
• Consider removing preloaded associations and lazily loading more data from the client via API (either REST or GraphQL): #331187 (comment 1752019722)

Process and Exit Criteria

1. Investigate performance problems with the Pipelines page on gitlab-org/gitlab: https://gitlab.com/gitlab-org/gitlab/-/pipelines, specifically looking at how we can address the remaining concerns from #329798 (comment 575428501)
2. Add lightly-researched proposals to Current Ideas
3. Write a technical proposals for the ideas that the team finds most promising as separate issues, assigned to the team most appropriate and able to work on that change.
4. See if the responses are "good" (this, as exit criteria, could use some refinement)
5. Close the spike, or rinse and repeat?