I assume that ECS Fargate would solve this, because one misbehaving ECS task would not affect others, and stopping it should still respect the shutdown routines.
Fargate is very expensive at scale. Great for small or bursty workloads, but when you’re at Figma scale, you almost always go EC2 for cost-effectiveness.
this isn't really true. It was very expensive when it was first released but now it's pretty cost competitive with EC2, especially when you consider easier scale down/up.
I think when you are at Figma scale you should have learned to keep things simpler. At this point I don’t think the (slightly) lower costs of EC2 weigh up against the benefits of Fargate.