- A
The target group's deregistration delay is too short.
Why wrong: Deregistration delay handles connection draining, not session creation.
- B
The stickiness duration is set too long, causing requests to be routed to terminated instances.
Why wrong: Stickiness duration is not the issue; the problem is that new instances lack session state.
- C
The Auto Scaling group's scale-in policy is terminating instances with active sessions.
Stickiness ties sessions to instances; if an instance is terminated, users lose session data. The correct fix is to externalize session state.
- D
The ALB health check is not configured for the new instances.
Why wrong: Health checks would mark instances unhealthy, not cause errors.
Question 1,658 of 1,746
Sticky Sessions Deployment Errors: Avoiding User Impact During Auto Scaling
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. 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 has a web application behind an Application Load Balancer that uses sticky sessions. The application is deployed on EC2 instances in an Auto Scaling group. During a deployment, the team notices that users are experiencing errors after new instances are launched. 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 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
✓
The Auto Scaling group's scale-in policy is terminating instances with active sessions.
Option C is the correct answer. The issue occurs during deployment when new instances are launched. With sticky sessions enabled, user sessions are tied to specific instances. If the Auto Scaling group's scale-in policy terminates instances that have active sessions (e.g., during a rolling update or instance replacement), users lose their session data and experience errors. Option A is incorrect because the deregistration delay is about waiting for in-flight requests to complete, not about session stickiness. Option B is incorrect because if stickiness duration were too long, requests would still be routed to terminated instances, but the issue here is after new instances are launched (scale-out), not scale-in. Option D is incorrect because health checks are configured and would pass for new healthy instances; the errors stem from missing session data on the new instances.
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's deregistration delay is too short.
Why it's wrong here
Deregistration delay handles connection draining, not session creation.
- ✗
The stickiness duration is set too long, causing requests to be routed to terminated instances.
Why it's wrong here
Stickiness duration is not the issue; the problem is that new instances lack session state.
- ✓
The Auto Scaling group's scale-in policy is terminating instances with active sessions.
Why this is correct
Stickiness ties sessions to instances; if an instance is terminated, users lose session data. The correct fix is to externalize session state.
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 ALB health check is not configured for the new instances.
Why it's wrong here
Health checks would mark instances unhealthy, not cause errors.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which SAP-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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Continuous Improvement for Existing Solutions — study guide chapter
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FAQ
Questions learners often ask
What does this SAP-C02 question test?
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Auto Scaling group's scale-in policy is terminating instances with active sessions. — Option C is the correct answer. The issue occurs during deployment when new instances are launched. With sticky sessions enabled, user sessions are tied to specific instances. If the Auto Scaling group's scale-in policy terminates instances that have active sessions (e.g., during a rolling update or instance replacement), users lose their session data and experience errors. Option A is incorrect because the deregistration delay is about waiting for in-flight requests to complete, not about session stickiness. Option B is incorrect because if stickiness duration were too long, requests would still be routed to terminated instances, but the issue here is after new instances are launched (scale-out), not scale-in. Option D is incorrect because health checks are configured and would pass for new healthy instances; the errors stem from missing session data on the new instances.
What should I do if I get this SAP-C02 question wrong?
Identify which SAP-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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Last reviewed: Jun 20, 2026
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