Though there are a couple articles on this, Apple's own security whitepaper actually acknowledges the use of Amazon S3 and Azure (page 41 as of 11/2/15): http:

Though there are a couple articles on this, Apple's own security whitepaper actually acknowledges the use of Amazon S3 and Azure (page 41 as of 11/2/15): http://www.apple.com/business/docs/iOS_Security_Guide.pdf http://www.apple.com/business/docs/iOS_Security_Guide.pdf Also, if you have a Mac (or I believe the PC iCloud app now supports iCloud Photo Library uploads), you can watch your network traffic, and last time I checked it also was connecting to some Amazon/AWS domains[1]. [1]: Others have also found the same-- http://appinstructor.com/blog/2015/apple-using-amazon-s3-storage-for-icloud-photo-library-storage http://appinstructor.com/blog/2015/apple-using-amazon-s3-sto...