AWS Certified SysOps Administrator – Associate (legacy) — Question 709

An application running on Amazon EC2 instances in an Auto Scaling group across multiple Availability Zones was deployed using an AWS CloudFormation template. The SysOps team has patched the Amazon Machine Image (AMI) version and must update all the EC2 instances to use the new AMI.
How can the SysOps Administrator use CloudFormation to apply the new AMI while maintaining a minimum level of active instances to ensure service continuity?

Answer options

• A. Run the aws cloudfomation update-stack command with the ג€" rollback-configuration option
• B. Update the CloudFormation template with the new AMI ID, then reboot the EC2 instances
• C. Deploy a second CloudFormation stack and use Amazon Route 53 to redirect traffic to the new stack
• D. Set an AutoScalingUpdate policy in the CloudFormation template to update the stack.

Correct answer: D

Explanation

Defining an AutoScalingUpdate policy in the CloudFormation template allows the stack to perform rolling updates on the Auto Scaling group, ensuring that a specified minimum number of instances remain operational throughout the update process. Simply rebooting instances as in Option B will not provision them with the new AMI, and Option A only governs rollback behavior. Option C is incorrect because deploying a completely new stack and using Amazon Route 53 is a blue/green deployment strategy that bypasses the native rolling update capabilities of CloudFormation for the existing stack.