I'm very very pro devops. But I am cautious about auto scale.

It adds a lot of complexity. If your app has predprtable load it may simplify stuff a lot to not auto scale. Think a b2b app with manual account creation. You know your user levels. 0 reason to turn on auto scale.

...so you run the servers you need for peak load 24/7? Ew. So much money just thrown away because "it's too complicated". We just scale based off of Network Out and only really spent a week finding the right threshold.

How long does your stack take to add a server. 3 minutes?

I have created a lot of services that couldn't have crappy perf for 3 minutes every time the load scales. Especially since in many apps the most expensive part is storage and dbs which cannot auto scale.

So say you spend 1k a month in your dbs and $100 for peak web load. You could spend a week fixing auto scaling bugs and try to save $25 by scaling web nodes down... But then you still have bad perf every time load spikes. I would not do that to save $25. I would question a company I work for that did that.

You need to be scaling up and down for hundreds of dollars per swing and have big spike loads before you add the complexity of auto scale.

We're sensitive enough that we preemptively scale as traffic "appears" to be increasing. So we add 5 EC2 instances, not at crisis levels of traffic, but "Hmmm...I feel a tingling in my extremities". We then remove one instance at a time if traffic falls below "Not doing anything" levels. The time between scaling actions is 15 minutes. Since ASG's go to remove older instances first, we don't end up getting charged a full hour for instances that are up for less than an hour that often.

Admittedly, our web traffic is very US Business Hours centric and peaks predictably between 3 and 4 in the afternoon.

Also, we're operating more at a scale of $40,000/month for peak traffic capacity 24/7 and $25,000/month once I got autoscaling worked out. So...yeah. I guess the scale for savings matters. :-)