I learned something in this interview that totally makes sense, but involved a scenario that didn't occur to me: If you're on one AWS service, or a customer of

I learned something in this interview that totally makes sense, but involved a scenario that didn't occur to me: If you're on one AWS service, or a customer of somebody else (like Heroku) who is on AWS, and you access another AWS service (they used an example of a 3rd party mysql provider), you don't incur bandwidth costs. I know right, no doy. I didn't realize there was such an ecosystem of providers built on top of AWS (who are providers themselves.)