Seem to finally sync correctly on iOS 15.2. But I am seeing a really annoying rate limiting in development environment, is this rate limiting also applying in production environment ? Because if that's the case initial sync will take an enormous amount of time considering how much I am storing in core data and a rate limiting of 70-80 seconds...

Most likely the same problem as here: https://developer.apple.com/forums/thread/687877 Me and other people with large core data store (and lot of relations) have been waiting since iOS 15 beta 4 for it to be fixed Let's hope it's fixed on iOS 15.1

Seems to be working as of now

Same here, kind of a bummer since I can't update my TestFlight build to work with latest iOS 15 beta :/