- A
Set the 'Reroute traffic to replacement instances' to 'Immediately'.
Why wrong: This shifts traffic to the new instances immediately without waiting for health checks, which could route requests to unhealthy instances and cause errors.
- B
Set the 'Reroute traffic to replacement instances' to 'Wait for time' and specify a wait time.
Why wrong: This waits for a fixed duration before rerouting traffic, but does not guarantee that instances have passed health checks; they might still be unhealthy after the wait period.
- C
Set the 'Reroute traffic to replacement instances' to 'Wait for health check' and specify the ELB health check.
This configuration ensures that new instances must pass the ELB health check before traffic is rerouted, meeting the requirement of routing traffic only to healthy instances.
- D
Set the deployment to terminate the original instances before rerouting traffic.
Why wrong: Terminating original instances before rerouting traffic would cause downtime because no instances are available to serve traffic during the transition.
Quick Answer
The correct answer is to set the 'Reroute traffic to replacement instances' to 'Wait for health check' and specify the ELB health check. This configuration is essential because it instructs CodeDeploy to hold traffic rerouting until the new instances in the blue/green deployment have been registered with the Application Load Balancer and have passed its health checks, ensuring only healthy targets receive traffic. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how CodeDeploy integrates with Elastic Load Balancing to achieve zero-downtime deployments. A common trap is assuming that simply registering instances is enough, but the key is the explicit wait for health check verification before rerouting. Remember it as "Healthy before Handoff" — the green fleet must pass its check before the blue fleet is retired.
DVA-C02 Deployment Practice Question
This DVA-C02 practice question tests your understanding of deployment. 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 developer is deploying a new version of a web application to an EC2 Auto Scaling group using AWS CodeDeploy with a blue/green deployment strategy. The Auto Scaling group is associated with an Application Load Balancer (ALB). The developer wants to ensure that the new instances are registered with the ALB and pass health checks before any traffic is routed to them. Which CodeDeploy configuration should the developer use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Set the 'Reroute traffic to replacement instances' to 'Wait for health check' and specify the ELB health check.
Option C is correct because setting 'Reroute traffic to replacement instances' to 'Wait for health check' and specifying the ELB health check ensures that CodeDeploy waits for the new instances to pass the ALB health checks before rerouting traffic. This aligns with the requirement that new instances must be registered and healthy before receiving traffic, preventing downtime or routing to unhealthy targets.
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.
- ✗
Set the 'Reroute traffic to replacement instances' to 'Immediately'.
Why it's wrong here
This shifts traffic to the new instances immediately without waiting for health checks, which could route requests to unhealthy instances and cause errors.
- ✗
Set the 'Reroute traffic to replacement instances' to 'Wait for time' and specify a wait time.
Why it's wrong here
This waits for a fixed duration before rerouting traffic, but does not guarantee that instances have passed health checks; they might still be unhealthy after the wait period.
- ✓
Set the 'Reroute traffic to replacement instances' to 'Wait for health check' and specify the ELB health check.
Why this is correct
This configuration ensures that new instances must pass the ELB health check before traffic is rerouted, meeting the requirement of routing traffic only to healthy instances.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Set the deployment to terminate the original instances before rerouting traffic.
Why it's wrong here
Terminating original instances before rerouting traffic would cause downtime because no instances are available to serve traffic during the transition.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse 'Wait for time' (a simple delay) with 'Wait for health check' (which actually verifies instance health), leading them to choose Option B, but only Option C guarantees that health checks pass before traffic is rerouted.
Detailed technical explanation
How to think about this question
Under the hood, CodeDeploy uses the ALB's target group health checks (e.g., HTTP/HTTPS ping on a specific path) to determine instance readiness. The 'Wait for health check' option leverages the ELB's health check mechanism, which includes configurable intervals, thresholds, and timeouts, ensuring instances are fully bootstrapped and responsive. In a real-world scenario, this prevents issues like serving stale content or failing requests during deployment, especially when new instances require time to warm up caches or connect to databases.
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.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Deployment — This question tests Deployment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set the 'Reroute traffic to replacement instances' to 'Wait for health check' and specify the ELB health check. — Option C is correct because setting 'Reroute traffic to replacement instances' to 'Wait for health check' and specifying the ELB health check ensures that CodeDeploy waits for the new instances to pass the ALB health checks before rerouting traffic. This aligns with the requirement that new instances must be registered and healthy before receiving traffic, preventing downtime or routing to unhealthy targets.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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