In trying to understand how Parse indexes work with Mongo, I noticed that some of my slow queries were using the _rperm field (from the ACL) even though I didn't specify it in the indexes that I defined. It isn't on every query either so I'm wondering why some queries need _rperm indexed and some don't.
If I query by just the id, the index seems to require
{"_id": 1, "_rperm": 1} and not just the {"_id": 1} index that is already defined.
What does parse do in the background to add _rperm and when do I need to include it as an index?