I think they are using the term 'capacity' to mean 'spare capacity'. I.e. that Amazon's entire compute usage is 80x the spare capacity, so scaling even a small amount would consume any spare capacity in AWS. Still, it seems hard to believe.
1. he misspoke and meant "80%" of the AWS capacity, which I agree seems implausible.
2. Amazon does not run on AWS because Amazon is 80x more than all of AWS infrastructure. This also seems implausible because of Netflix. In fact, there's an article out there that said AWS exceeded Amazon's capacity within 1 quarter!
I still don't understand what that has to do with autoscaling exactly
I did’t understand either. I suspect it’s the semantic difference between ‘public cloud’ and ‘infrastructure’. I don’t know what that difference is really.