Bug: project/:id/results endpoint is slow

[MichaelAkvo]

What were you doing?

When using the new code using project hierarchies, the endpoint became slower.
Open the overview of a program with a lot of projects e.g https://rsr.akvo.org/my-rsr/programs/7350

Waited for a long time for it to load.

What should've happened?

It should've been faster than before, but instead it's slower.

My environment

No response

Additional context

The old code was optimized for its old data model. Now it has to be updated for the new hierarchies.

The relevant endpoint is /rest/v1/project/:id/results/