>We're starting to ramp up traffic now by orders of magnitude (with many more to come) and it's soooooo awesome knowing the stack is pretty much bombproof.

This does come with additional cost. Serverless pricing doesn't scale, your costs increase linearly with your usage, and there're no discounts for bulk usage or reserved pricing.

We were recently on the receiving end of a massive HTTP GET Flood DDoS and although we did not experience any downtime as a result of it, I ended up finding out about it a few days later when billing alarms started going off.