Autoscaling sounds great, but in practice it notices that there is a problem after you already have once, and by the time you've scaled up, there is no problem any more. Which is the worst of all worlds.
For example in this case you'd realize there is a problem at the top of the hour. And 2 minutes later you'd have a bunch of autoscaled instances up, all wondering what the fuss was about. So they scale down again, but then at the top of the next hour the same thing happens again with the same result.
The same thing happens with ad servers. An ad buy goes in for 30 seconds. When it hits, you have a firehose. That then shuts off.
In fact this problem is so common that I recommend against autoscaling unless you have specific reason to believe that it will work for you.