Apple is sending out emails reminding developers that CloudKit will require the latest developer previews of either iOS 8 or OS X Yosemite to work starting tomorrow. While both developer previews were released today, starting Tuesday July 22 they will be required for developers who use CloudKit.
In addition, Apple is also recommending that developers backup their public databases as they will be performing a server-side wipe. This will not affect iCloud Drive, iCloud Photo Library, or Mail Drop as those were already wiped earlier this one.
"We will perform a server-side data wipe on all CloudKit public databases on July 22," the company's email reads. "If you are using iCloud containers with public databases, consider creating a copy of your data so that you can re-upload once the data wipe is complete. iCloud Drive, iCloud Photo Library, and Mail Drop will not be impacted by the targeted data wipe."
CloudKit was announced at this year's WWDC to allow developers to more easily work with server-side data.