The answer is a health check grace period that is too short for the Auto Scaling group. This is the most likely cause because when CodeDeploy deploys a new application version to instances in an Auto Scaling group, the Elastic Load Balancer begins routing traffic and performing health checks immediately after the instance passes its initial state. If the grace period expires before the application’s startup scripts finish executing, the load balancer marks the instance as unhealthy and deregisters it, causing CodeDeploy to report a deployment failure due to too few healthy instances—even though the AppSpec scripts ran successfully on some instances. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how Auto Scaling health checks interact with CodeDeploy lifecycle hooks; a common trap is to blame the AppSpec file or instance configuration when the real issue is timing. Remember the mnemonic “Grace before Health”—always ensure the grace period covers the full application startup window to avoid false negatives.
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An organization uses AWS CodeDeploy to deploy a web application to an Auto Scaling group. The deployment fails with the error 'The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available for deployment, or some instances in your deployment group are experiencing problems.' The engineer reviews the deployment logs and finds that the AppSpec file is correctly formatted and the scripts run successfully on some instances. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The health check grace period for the Auto Scaling group is too short.
Option B is correct because if health check grace period is too short, instances might be marked unhealthy before the application starts. Option A would affect all instances. Option C would cause consistent failures. Option D might not cause instance failure.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The CodeDeploy agent is not installed on some instances.
Why it's wrong here
This would cause failures on those instances, consistent across deployments.
✗
The target group is not configured to route traffic to the instances.
Why it's wrong here
This would not cause instance deployment failures.
✓
The health check grace period for the Auto Scaling group is too short.
Why this is correct
Instances may be terminated before the application starts, causing deployment failure.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The IAM role assigned to the EC2 instances does not have sufficient permissions.
Why it's wrong here
This would cause consistent failures on all instances.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The health check grace period for the Auto Scaling group is too short. — Option B is correct because if health check grace period is too short, instances might be marked unhealthy before the application starts. Option A would affect all instances. Option C would cause consistent failures. Option D might not cause instance failure.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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