It seems CKQuerySubscription cannot be used for subscribing to shared DB changes in cloud kit. CKDatabaseSubscription neither works nor does CKSubscription
How can I achieve subscribing to Shared DB changes?
Simply. How can i achive a notification about change made on record that is shared with me. I AM NOT THE OWNER OF THE RECORD.
Related question is here:
How to receive cloudkit notifications about changes made on record shared with me?
Turns out, its not possible to subscribe on a zone level or a record level for Shared DB in CloudKit. Ref: https://developer.apple.com/library/content/qa/qa1917/_index.html
Be aware that CKQuerySubscription is not supported in the shared database, and
CKDatabaseSubscription currently only tracks the changes from custom zones in the private and shared database.