https://www.cnbc.com/2018/02/26/apple-confirms-it-uses-google-cloud-for-icloud.html

A file that Apple updated on its website last month provides the first acknowledgment that it's relying on Google's public cloud for data storage for its iCloud services.

The disclosure is fresh evidence that Google's cloud has been picking up usage as it looks to catch up with the likes of Amazon and Microsoft in the cloud infrastructure business.