- A
The Auto Scaling group is scaling too aggressively, causing thrashing.
Why wrong: Incorrect. If the Auto Scaling group were thrashing, you would see high CPU utilization as instances are launched and terminated frequently, not consistently low CPU.
- B
The Application Load Balancer has a sticky session configuration that is not distributing traffic evenly.
Why wrong: Incorrect. Sticky sessions can cause uneven traffic distribution, leading to some instances having high CPU while others are low. The question states average CPU is below 20%, which doesn't indicate uneven distribution.
- C
The application database is under-provisioned and is causing slow query responses.
Correct. A database bottleneck can cause slow application performance without high EC2 CPU, as the application servers spend time waiting for database responses.
- D
The EC2 instances are using burstable performance and have exhausted their CPU credits.
Why wrong: Incorrect. If burstable instances exhaust CPU credits, they are throttled to baseline performance, which would still result in low CPU utilization but might explain slow performance. However, the most likely cause given common scenarios is a database bottleneck, not CPU credit exhaustion, because low CPU is more typically associated with waiting on external resources.
SOA-C02 Bottleneck Practice Question
This SOA-C02 practice question tests your understanding of cost and performance optimization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: bottleneck. 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 SysOps administrator is troubleshooting slow application performance. The application runs on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. Amazon CloudWatch metrics show that the average CPU utilization across the instances is below 20%, but the application is still slow. What is the MOST likely cause of the performance issue?
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 application database is under-provisioned and is causing slow query responses.
The most likely cause is that the application database is under-provisioned, leading to slow query responses. Even though EC2 CPU utilization is low, the application performance is bottlenecked by database latency. This is a common scenario where the database tier is the constraint, not the compute tier.
Key principle: Bottleneck
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 Auto Scaling group is scaling too aggressively, causing thrashing.
Why it's wrong here
Incorrect. If the Auto Scaling group were thrashing, you would see high CPU utilization as instances are launched and terminated frequently, not consistently low CPU.
- ✗
The Application Load Balancer has a sticky session configuration that is not distributing traffic evenly.
Why it's wrong here
Incorrect. Sticky sessions can cause uneven traffic distribution, leading to some instances having high CPU while others are low. The question states average CPU is below 20%, which doesn't indicate uneven distribution.
- ✓
The application database is under-provisioned and is causing slow query responses.
Why this is correct
Correct. A database bottleneck can cause slow application performance without high EC2 CPU, as the application servers spend time waiting for database responses.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Bottleneck
- ✗
The EC2 instances are using burstable performance and have exhausted their CPU credits.
Why it's wrong here
Incorrect. If burstable instances exhaust CPU credits, they are throttled to baseline performance, which would still result in low CPU utilization but might explain slow performance. However, the most likely cause given common scenarios is a database bottleneck, not CPU credit exhaustion, because low CPU is more typically associated with waiting on external resources.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates may assume low CPU means the compute layer is fine, but the real bottleneck could be the database tier. Don't automatically rule out downstream components.
Trap categories for this question
Scenario analysis trap
Incorrect. If burstable instances exhaust CPU credits, they are throttled to baseline performance, which would still result in low CPU utilization but might explain slow performance. However, the most likely cause given common scenarios is a database bottleneck, not CPU credit exhaustion, because low CPU is more typically associated with waiting on external resources.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Bottleneck
- CPU Utilization
- Database Provisioning
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
Bottleneck
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review bottleneck, then practise related SOA-C02 questions on the same topic to reinforce the concept.
- →
Cost and Performance Optimization — study guide chapter
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Cost and Performance Optimization practice questions
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Cost and Performance Optimization — This question tests Cost and Performance Optimization — Bottleneck.
What is the correct answer to this question?
The correct answer is: The application database is under-provisioned and is causing slow query responses. — The most likely cause is that the application database is under-provisioned, leading to slow query responses. Even though EC2 CPU utilization is low, the application performance is bottlenecked by database latency. This is a common scenario where the database tier is the constraint, not the compute tier.
What should I do if I get this SOA-C02 question wrong?
Review bottleneck, then practise related SOA-C02 questions on the same topic to reinforce the concept.
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?
Bottleneck
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Last reviewed: Jun 20, 2026
This SOA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SOA-C02 exam.
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