Jeff’s Note #
Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.
For DVA-C02 candidates, the confusion often lies in how to manage infrastructure as code resources referencing region-specific IDs like AMIs. In production, this is about knowing exactly how AMIs must exist in the region where the stack launches and using efficient automation to avoid manual errors or duplicated efforts. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
CloudSprint Solutions run a customer-facing web portal deployed on Amazon EC2 instances. They use a custom Amazon Machine Image (AMI) created and maintained regularly in the us-east-1 region. The infrastructure deployment is automated with AWS CloudFormation templates.
The company is expanding to the us-west-1 region and wants to deploy the exact same environment using the existing CloudFormation templates. However, attempts to create the stack in the us-west-1 region fail with an error indicating that the specified AMI ID does not exist in that region.
The Requirement: #
A developer needs to fix the deployment failure caused by the missing AMI in us-west-1, using the solution with the least operational overhead and without manually provisioning the environment outside of CloudFormation.
The Options #
- A) Modify the CloudFormation templates for both us-east-1 and us-west-1 to use an official AWS AMI instead of the custom AMI, then redeploy stacks in both regions.
- B) Copy the existing custom AMI from us-east-1 to us-west-1. Update the CloudFormation template for us-west-1 to reference the new AMI ID in us-west-1, then redeploy the stack.
- C) Build a new custom AMI manually in us-west-1. Create a new CloudFormation template with the new AMI ID and deploy the stack in us-west-1.
- D) Skip using CloudFormation and deploy the application manually in us-west-1.
Google adsense #
leave a comment:
Correct Answer #
B
Quick Insight: The Developer Imperative #
The key in this scenario is understanding that AMIs are region-specific resources and must exist in the target region for CloudFormation to reference them. AWS provides a seamless way to copy AMIs across regions with minimal overhead, ensuring infrastructure as code (IaC) deployments remain automated and consistent.
Content Locked: The Expert Analysis #
You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?
The Expert’s Analysis #
Correct Answer #
Option B
The Winning Logic #
Custom AMIs created in one region do not automatically exist in other regions. Since CloudFormation templates use the AMI ID as a parameter when launching EC2 resources, that AMI must exist in the deployment region. Copying the AMI across regions preserves the exact desired image, and updating the template to reference the new AMI ID allows the stack to launch successfully.
This approach avoids building an entirely new AMI from scratch (which adds development and QA overhead), and keeps the deployment fully automated and reproducible within CloudFormation. It also avoids manual deployments, which are error-prone and do not scale well.
The Trap (Distractor Analysis) #
-
Why not A? Using a public AWS AMI removes dependency on your custom image but changes the environment and application baseline, potentially breaking functionality and not meeting requirements.
-
Why not C? Building a new AMI in the second region requires manual build processes and maintaining separate images, increasing operational complexity and risking drift.
-
Why not D? Manual deployments break infrastructure as code principles, causing poor repeatability and increased error risk.
The Technical Blueprint #
Useful AWS CLI command to copy AMI cross-region: #
aws ec2 copy-image \
--source-image-id ami-1234567890abcdef0 \
--source-region us-east-1 \
--region us-west-1 \
--name "CopiedCustomAMI-us-west-1"
Update your CloudFormation template parameter or mapping for Region to use the copied AMI ID in us-west-1 before deploying.
The Comparative Analysis #
| Option | API Complexity | Performance | Use Case |
|---|---|---|---|
| A | Low | High risk | Simplifies images but breaks app baseline |
| B | Medium | Optimal | Maintains image consistency, minimal overhead |
| C | High | Moderate | Time-consuming, manual AMI build |
| D | None | Poor | Manual deployment, no IaC automation |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always remember: Custom AMIs must be available in the deployment region, and AWS provides the copy-image API to efficiently handle this.
Real World #
In production, CI/CD pipelines often automate AMI building and cross-region copying to keep environments consistent globally without manual steps.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the DVA-C02 exam.