We currently serve some static files with Fastly from a S3 bucket as a backend.
I know Fastly has some optimizations between the Fastly network and AWS’s.
Would enabling S3 Transfer Acceleration be faster for cold objects? Obviously it would not change a thing for objects already cached by Fastly.
More info about S3 Transfer Acceleration: http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html