A company asks you to deploy an existing application into four additional AWS Regions. The application currently runs on over 100 EC2 instances in us-east-1 and uses fully configured AMIs. A CloudFormation template exists that deploys the stack in us-east-1. What is the most operationally efficient way to deploy the application into the other Regions?

The most operationally efficient method is to copy the existing AMI to each target Region using aws ec2 copy-image. This preserves the fully configured state of the application. Then, update the CloudFormation template to use Mappings. Mappings allow you to define different AMI IDs for different Regions within a single template, making it reusable across all target Regions without modification. Taking snapshots and creating new AMIs is a multi-step process that is less efficient than directly copying the AMI. Running the same CloudFormation template without modification will fail because AMI IDs are Region-specific. CloudFormation cannot deploy resources across multiple Regions from a single stack update; it operates within a single Region.