PERF: skip existing users if large no of notifications expected (PR #9061)

We shouldn’t update default categories for existing users if large no. of notifications are expected.


More details at

This seems good to me. We should wait to merge though until stable is in a good place.


This is a handy trick in case the case is re-evaluated for any reason.

sorry @vinothkannans I am closing this as a bit too risky, we have sat on this for quite a while and it churns through some very very critical code. I prefer to hold off on this risk.