The correct actions are to gradually shift traffic from the old environment to the new environment using the ALB, and to fully test the new environment before shifting traffic. This works because a blue/green deployment with zero downtime relies on keeping the old (blue) environment fully active while the new (green) environment is created, tested, and then traffic is incrementally routed to it via the Application Load Balancer’s target group. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of CodeDeploy’s deployment lifecycle and the critical role of the ALB in traffic shifting. A common trap is assuming you should terminate old instances immediately or update instances in-place, which would break the zero-downtime guarantee. Remember the memory tip: "Test green, shift traffic, keep blue alive" — never destroy the old environment until the new one is verified and traffic is fully migrated.
DVA-C02 Deployment Practice Question
This DVA-C02 practice question tests your understanding of deployment. 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.
A company is deploying a new web application on Amazon EC2 instances behind an Application Load Balancer. The application must be deployed with no downtime. The deployment uses AWS CodeDeploy with a Blue/Green deployment configuration. Which TWO actions should be taken to achieve zero-downtime deployment? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a new Auto Scaling group with the new application version and register it with the ALB.
Options A and D are correct. A: If the new environment passes tests, traffic is shifted to it. D: Before shifting traffic, the new environment must be fully tested. Option B is wrong because terminating old instances immediately would cause downtime if the new environment fails. Option C is wrong because the new environment should be created first, not updated in-place. Option E is wrong because the load balancer is already in place; you should register the new instances with the existing ALB.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create a new load balancer for the new environment.
Why it's wrong here
The existing ALB can be used for both environments.
✓
Create a new Auto Scaling group with the new application version and register it with the ALB.
Why this is correct
This creates the new environment for testing.
Related concept
Static NAT maps one inside address to one outside address.
✗
Update the existing Auto Scaling group with the new application version.
Why it's wrong here
Blue/Green uses separate environments, not in-place update.
✗
Terminate the old EC2 instances immediately after deploying the new ones.
Why it's wrong here
This would cause downtime if the new environment fails.
✓
Gradually shift traffic from the old environment to the new environment using the ALB.
Why this is correct
Blue/Green deployment shifts traffic gradually.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DVA-C02 NAT questions on configuration and troubleshooting.
Deployment — This question tests Deployment — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Create a new Auto Scaling group with the new application version and register it with the ALB. — Options A and D are correct. A: If the new environment passes tests, traffic is shifted to it. D: Before shifting traffic, the new environment must be fully tested. Option B is wrong because terminating old instances immediately would cause downtime if the new environment fails. Option C is wrong because the new environment should be created first, not updated in-place. Option E is wrong because the load balancer is already in place; you should register the new instances with the existing ALB.
What should I do if I get this DVA-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DVA-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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