I don’t know any write ups, but in short, AWS was a solution to the variable demand for Amazon’s, well, web services. Demand peaked considerably during holiday shopping months but otherwise remained far too low to justify keeping all of those peak demand servers running Amazon.com full time, so they were rented out to companies that actually had similar problems of peak demand. In particular, the Victoria’s Secret fashion show is a great example of extreme peak demand and scalability for a web service that otherwise attracts relatively little traffic most of the year.