A company runs an application on Amazon EC2 instances.

The key requirement is to meet an RTO of less than 4 hours while using as few resources as possible during normal operations. A backup-and-restore style DR approach using AMIs in a secondary Region aligns with that goal, and AWS CloudFormation is the most operationally efficient way to automate rebuilding the environment. AWS disaster recovery guidance describes backup-and-restore as the lowest-cost pattern during steady state because compute resources are not running in the recovery Region until needed. CloudFormation is preferable to custom scripts because it gives repeatable infrastructure deployment with less custom operational code. Keeping instances active in another Region or AZ would consume more resources during normal operations than necessary.

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