The answer is that the target group associated with the Auto Scaling group is not properly configured to route traffic. In a CodeDeploy Blue/Green deployment, the new instances are launched and pass health checks, but traffic routing depends entirely on the load balancer’s target group and its listener rules. If the target group lacks correct forwarding rules, has a deregistration delay that prevents traffic from reaching the new instances, or uses overly strict health check thresholds, the instances will remain healthy but unreachable. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how CodeDeploy integrates with Elastic Load Balancing—specifically, that a successful deployment lifecycle does not guarantee traffic flow. A common trap is assuming that passing instance health checks automatically routes traffic; in reality, the load balancer must actively forward requests to the new target group. Memory tip: “Health checks pass, but traffic stays—check the listener rules and target group.”
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A team uses AWS CodeDeploy to deploy a web application to an Auto Scaling group. The deployment strategy is Blue/Green. During a recent deployment, the new instances passed all health checks, but traffic was not routed to them. What is the most likely reason?
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 target group associated with the Auto Scaling group is not properly configured to route traffic.
In a Blue/Green deployment with CodeDeploy and an Auto Scaling group, traffic routing is handled by a load balancer target group. If the target group is not properly configured to route traffic to the new instances (e.g., missing or incorrect listener rules, deregistration delay, or health check thresholds), the instances may pass health checks but never receive traffic. This is the most likely cause because the deployment succeeded in provisioning and validating the new instances, but the load balancer did not forward requests to them.
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 target group associated with the Auto Scaling group is not properly configured to route traffic.
Why this is correct
The target group must be correctly set up to forward traffic to the new instances.
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 deployment group is not configured to use a load balancer.
Why it's wrong here
Blue/Green deployments require a load balancer; if not configured, CodeDeploy would not proceed.
✗
The Auto Scaling group's lifecycle hook failed to signal readiness.
Why it's wrong here
Lifecycle hooks affect instance state but not traffic routing directly.
✗
The CodeDeploy agent on the new instances is not installed.
Why it's wrong here
If the agent were missing, CodeDeploy would report a failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume health check success guarantees traffic routing, but in AWS, health checks only verify instance readiness; traffic routing depends on separate load balancer listener rules and target group associations.
Detailed technical explanation
How to think about this question
Under the hood, CodeDeploy Blue/Green deployments for Auto Scaling groups use a load balancer to shift traffic by updating the target group's registered targets or modifying listener rules. The target group's health check settings (e.g., protocol, path, interval, threshold) must align with the application's actual health endpoint; if the health check succeeds but the listener rule does not point to the correct target group, traffic is never forwarded. A real-world scenario is when the target group is associated with the wrong listener (e.g., HTTP:80 instead of HTTPS:443) or the deregistration delay causes the old target group to remain active.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 target group associated with the Auto Scaling group is not properly configured to route traffic. — In a Blue/Green deployment with CodeDeploy and an Auto Scaling group, traffic routing is handled by a load balancer target group. If the target group is not properly configured to route traffic to the new instances (e.g., missing or incorrect listener rules, deregistration delay, or health check thresholds), the instances may pass health checks but never receive traffic. This is the most likely cause because the deployment succeeded in provisioning and validating the new instances, but the load balancer did not forward requests to them.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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