← SOA-C02·Amazon Web Services

Question 887 of 1,546

Cost and Performance Optimization →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is an under-provisioned database causing slow query responses. This is correct because when the application database is the bottleneck, the EC2 instances spend most of their time waiting for data rather than processing it, which explains why CloudWatch shows low CPU utilization below 20% despite slow application performance. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your ability to distinguish between compute and database bottlenecks—a common trap is assuming low CPU always means the application is fine, when in reality the database contention is throttling throughput. Remember that database bottlenecks often manifest as high connection counts, elevated read/write latency, or increased swap usage on the RDS instance, while the application servers remain idle. A useful memory tip: "Low CPU, slow app? Check the database stack."

SOA-C02 Cost and Performance Optimization 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. 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 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.

Question 1mediummultiple choice

Full question →

A
The Auto Scaling group is scaling too aggressively, causing thrashing.
Why wrong: Thrashing would cause high CPU as instances are launched and terminated.
B
The Application Load Balancer has a sticky session configuration that is not distributing traffic evenly.
Why wrong: Sticky sessions do not cause low CPU across all instances.
C
The application database is under-provisioned and is causing slow query responses.
A database bottleneck can cause slow performance despite low app server CPU.
D
The EC2 instances are using burstable performance and have exhausted their CPU credits.
Why wrong: Exhausted credits would throttle CPU, but CPU utilization would be low? Actually, it would limit CPU to baseline, potentially causing slowdowns, but the CPU metric would show low utilization because the CPU is throttled. However, this is also plausible, but database bottleneck is more typical for application slowness with low CPU. However, as per AWS best practices, when CPU is low and app is slow, check database. Option D is a distractor that might be chosen by those who know T instances.

Full breakdown with real-world context →

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.

Option B is correct because if the database is the bottleneck, even if the application servers have low CPU usage, the overall performance can be slow due to database contention. Option A is wrong because if the ALB is not distributing traffic, some instances would have high CPU. Option C is wrong because low CPU utilization indicates that the application servers are not overloaded. Option D is wrong because burstable performance instances (T-series) have a CPU credit balance; if the balance is depleted, CPU performance is throttled, leading to low CPU but slow performance? Actually, when credits are exhausted, T instances provide baseline performance, which may be low, but CPU utilization would still be limited, not necessarily low; but more importantly, the symptoms match a database bottleneck.

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 Auto Scaling group is scaling too aggressively, causing thrashing.
Why it's wrong here
Thrashing would cause high CPU as instances are launched and terminated.
✗
The Application Load Balancer has a sticky session configuration that is not distributing traffic evenly.
Why it's wrong here
Sticky sessions do not cause low CPU across all instances.
✓
The application database is under-provisioned and is causing slow query responses.
Why this is correct
A database bottleneck can cause slow performance despite low app server CPU.
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 EC2 instances are using burstable performance and have exhausted their CPU credits.
Why it's wrong here
Exhausted credits would throttle CPU, but CPU utilization would be low? Actually, it would limit CPU to baseline, potentially causing slowdowns, but the CPU metric would show low utilization because the CPU is throttled. However, this is also plausible, but database bottleneck is more typical for application slowness with low CPU. However, as per AWS best practices, when CPU is low and app is slow, check database. Option D is a distractor that might be chosen by those who know T instances.

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.

Trap categories for this question

Command / output trap
Exhausted credits would throttle CPU, but CPU utilization would be low? Actually, it would limit CPU to baseline, potentially causing slowdowns, but the CPU metric would show low utilization because the CPU is throttled. However, this is also plausible, but database bottleneck is more typical for application slowness with low CPU. However, as per AWS best practices, when CPU is low and app is slow, check database. Option D is a distractor that might be chosen by those who know T instances.

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 SOA-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 SOA-C02 question test?

Cost and Performance Optimization — This question tests Cost and Performance Optimization — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The application database is under-provisioned and is causing slow query responses. — Option B is correct because if the database is the bottleneck, even if the application servers have low CPU usage, the overall performance can be slow due to database contention. Option A is wrong because if the ALB is not distributing traffic, some instances would have high CPU. Option C is wrong because low CPU utilization indicates that the application servers are not overloaded. Option D is wrong because burstable performance instances (T-series) have a CPU credit balance; if the balance is depleted, CPU performance is throttled, leading to low CPU but slow performance? Actually, when credits are exhausted, T instances provide baseline performance, which may be low, but CPU utilization would still be limited, not necessarily low; but more importantly, the symptoms match a database bottleneck.

What should I do if I get this SOA-C02 question wrong?

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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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.