Yep, you could also say Apple's CloudKit is another proprietary NoSQL solution for the purpose of providing more value and lock-in into the iOS ecosystem. But at least CloudKit has generous free usage up to:

   - 1PB for assets
   - 10TB for database

https://developer.apple.com/icloud/documentation/cloudkit-st...

Looks like you'll need 10 million users in order to have that much space, though.