AWS Certified SysOps Administrator – Associate (legacy) — Question 922

An Applications team has successfully deployed an AWS CloudFormation stack consisting of 30 t2-medium Amazon EC2 instances in the us-west-2 Region.
When using the same template to launch a stack in us-east-2, the launch failed and rolled back after launching only 10 EC2 instances.
What is a possible cause of this failure?

Answer options

• A. The IAM user did not have privileges to launch the CloudFormation template.
• B. The t2.medium EC2 instance service limit was reached.
• C. An AWS Budgets threshold was breached.
• D. The application's Amazon Machine Image (AMI) is not available in us-east-2.

Correct answer: D

Explanation

Amazon Machine Images (AMIs) are regional resources, meaning an AMI ID from us-west-2 is not valid in us-east-2 unless it has been copied to that region. If the CloudFormation template references a region-specific AMI ID that is missing in the target region, the stack launch will fail and roll back. Other issues like insufficient IAM permissions would have prevented the deployment from starting at all, rather than failing mid-way.