I'm aware of the API rate limit when an AZ goes down, but the original comment was about problems that people run into for highly-variable traffic sites that scale up and down on a regular basis (e.g. spin up 20 instances during the day with high traffic, at night shutdown 15 of them to save cost, on a daily basis). This of course is not related to any AZ/API downtime, and I am not aware of any problems that could interfere with the normal usage of APIs during normal service operations, which is why I wanted to hear more about the details of those problems.