CloudKit What's the developer cost for shared database?

What's the price model for the shared database, i.e. the record user shared with others.

Does the record user shared counting towards the app's public database quota?

Or does it remain in user's private database quota for whom shared that record?

In another word, would implement the sharing feature(without using the public database) lead to additional cost on the developer side?
CloudKit What's the developer cost for shared database?
 
 
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