I have a service in ECS. I am currently trying to turn everything off so I am not charged any more money. I have 0 pending and 0 running tasks. There was one registered container instance so I de-registered it. I also terminated the instance in EC2. However, a few minutes after deregistering and terminating the instance, I see that a new container instance is registered and a new running EC2 instance shows up in my dashboard. Why does the instance keep re-appearing and how do I make it stop?
It sounds like you have an Auto Scaling group that is launching new instances. The ECS documentation has a section on cleaning up.