have you tried prefetch_related too instead of select_related?

Select related performs an inner join and results in more data going over the wire between database and application, especially here because the joined form will always be same as the form we already retrieved (meaning that 55 logic rules result in 55 times the same form being joined).

For the trigger_from_step, I expect a similar situation - it's more likely that multiple different logic rules have the same trigger_from_step, so joining can be slower than doing a prefetch. And of course, the related form of the trigger_from_step has the same problem as the form FK of the logic rule.

I think that all three of these fields (form, trigger_from_step and trigger_from_step__form) might benefit from a prefetch - it will result in a couple more queries, but it will be a fixed amount and the data going over the wire could be a lot less, so I'm interested in the performance profile of that approach.

I didn't notice any difference concerning the update endpoints for both logic-rules and variables (tried with both joins and prefetch)

You specifically mention the update endpoints, but I'm interested in the list endpoints in particular :P

However, looking at your screenshots, prefetch_related seems to be a clear winner!

I think the variables bulk/list endpoint may have similar issues, iirc that one also showed up in APM. You can give it the same treatment (notably the FormVariable.form and FormVariable.form_definition foreign keys may cause n+1 queries here)

This is why I mentioned it.I understood that we wanted to see what's going on with these as well. But clearly wrong place to write this, it should be as a reply to the above.