You can create an Amazon Machine Image (AMI) to recover from an unexpected event or create a new Controller from the same image.

The AMI image should be created for the Controller, including required optimizations, and an auto-scaling group should be created based on the AMI. You can configure the Elastic Load Balancer (ELB) to send traffic to instances in the auto-scaling group, which will consist of one EC2 instance at a time.