Take 2 contents : Content A (article with an object relation field) and Content B :

• Edit A and add a relation to B using the objectRelation field.
• Repeat the first step X times with X different articles.
• Display A in the admin => the page will timeout (or take a very long time to load).

In my case X == 61k. I checked the ContentViewController code and displaying A will invoke loadReverseRelations() for each object linked to A. So it will load all reverse relations of B, giving more than 61k results.

As you can imagine, it becomes even more problematic when A has multiple relations like that.

I join a screenshot of the profiling using blackfire.