Exactly, you've answered yourself. Also nothing prevents you from using multi zoned auto scaling group with a min/max of 1, you'll fail over to another AZ grac

Exactly, you've answered yourself. Also nothing prevents you from using multi zoned auto scaling group with a min/max of 1, you'll fail over to another AZ gracefully. You don't magically get 9 nines with lambda in practice either, trust me.