Apple has expanded the capabilities of CloudKit, the company's server-side API and a component of iCloud, adding support for server-to-server web service requests. Interaction with the CloudKit public database has previously been restricted to apps on iPhone and iPad, Mac, and web.

From Apple:

In addition to providing a web interface for users to access the same data as your app, you can now easily read and write to the CloudKit public database from a server-side process or script with a server-to-server key. Learn more about generating a server-to-server key and composing web service requests.

CloudKit provides a number of tools to developers, including authentication services, private and public databases, and asset storage, letting developers focus more on the client-side components of their apps.

Source: Apple