The only way you are going to learn how these proprietary systems work are by working at Google or Amazon. What makes the EC2, S3, etc. APIs different from AppEngine or the 100s of other Google APIs there are? They're all just APIs to proprietary systems (well, except when writing apps for Chrome and Android). You are learning "how they work" only in the most superficial meaning of the phrase.
So... care to tell me how EC2 works? :P
The only way you are going to learn how these proprietary systems work are by working at Google or Amazon. What makes the EC2, S3, etc. APIs different from AppEngine or the 100s of other Google APIs there are? They're all just APIs to proprietary systems (well, except when writing apps for Chrome and Android). You are learning "how they work" only in the most superficial meaning of the phrase.