https://www.kodeco.com/3413-introduction-to-cloudkit/lessons/10
Learn how to use user accounts to determine the status of a user and to fetch data for the the user.
user accountsintroductioncloudkitepisode
https://www.macrumors.com/2014/07/04/apple-cloudkit-wipe-july-7/
Apple has notified developers of plans for a server-side data wipe on CloudKit public and private databases for both the beta versions iOS 8 and OS X Yosemite....
appleplanningwipecloudkitdata