- A
Perform a rolling update of the Auto Scaling group with a health check grace period.
Why wrong: Rolling updates replace instances incrementally, potentially terminating instances with active sessions.
- B
Use an immutable deployment by launching a new Auto Scaling group and then updating the ALB target group to point to the new group.
Why wrong: Switching all traffic at once drops in-flight sessions.
- C
Use a blue/green deployment: launch a new Auto Scaling group, register it with a new target group, and gradually shift traffic using weighted target groups on the ALB.
Gradual shift preserves sessions on old environment until they complete.
- D
Use a canary deployment with AWS Lambda to gradually route a percentage of requests to the new version.
Why wrong: Lambda is not suitable for stateful EC2 applications with sticky sessions.
Quick Answer
The answer is a blue/green deployment using weighted target groups on the ALB. This approach is correct because it launches a completely new Auto Scaling group and target group for the updated application, then gradually shifts traffic using the ALB’s weighted routing, which allows existing sticky sessions to complete on the old environment while new sessions are directed to the new one. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how to handle stateful applications with session affinity during zero-downtime deployments—a common trap is assuming a rolling update or immutable deployment works, but those drop in-flight sessions because they terminate instances before sessions finish. The key insight is that weighted target groups let you control traffic flow without breaking established sticky sessions. Memory tip: think “green for new, blue for old, weights control the hold”—the old environment stays alive until all sessions drain naturally.
DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 runs a stateful web application on EC2 instances behind an ALB. The application uses sticky sessions (session affinity) to maintain user sessions. During a deployment, the company wants to update the application with zero downtime and ensure that in-flight sessions are not lost. Which deployment strategy should they 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
Use a blue/green deployment: launch a new Auto Scaling group, register it with a new target group, and gradually shift traffic using weighted target groups on the ALB.
Option C is correct because a blue/green deployment with a new target group and a gradual shift of traffic using the ALB's weighted target groups allows existing sessions to complete on the old environment while new sessions go to the new one. Option A is wrong because rolling update with a fixed number of instances may cause session loss. Option B is wrong because immutable deployment without traffic shifting drops sessions. Option D is wrong because canary deployment with Lambda is not applicable to EC2.
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.
- ✗
Perform a rolling update of the Auto Scaling group with a health check grace period.
Why it's wrong here
Rolling updates replace instances incrementally, potentially terminating instances with active sessions.
- ✗
Use an immutable deployment by launching a new Auto Scaling group and then updating the ALB target group to point to the new group.
Why it's wrong here
Switching all traffic at once drops in-flight sessions.
- ✓
Use a blue/green deployment: launch a new Auto Scaling group, register it with a new target group, and gradually shift traffic using weighted target groups on the ALB.
Why this is correct
Gradual shift preserves sessions on old environment until they complete.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a canary deployment with AWS Lambda to gradually route a percentage of requests to the new version.
Why it's wrong here
Lambda is not suitable for stateful EC2 applications with sticky sessions.
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 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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. 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.
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.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a blue/green deployment: launch a new Auto Scaling group, register it with a new target group, and gradually shift traffic using weighted target groups on the ALB. — Option C is correct because a blue/green deployment with a new target group and a gradual shift of traffic using the ALB's weighted target groups allows existing sessions to complete on the old environment while new sessions go to the new one. Option A is wrong because rolling update with a fixed number of instances may cause session loss. Option B is wrong because immutable deployment without traffic shifting drops sessions. Option D is wrong because canary deployment with Lambda is not applicable to EC2.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
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