- A
The Auto Scaling policy for the Aurora cluster is set to scale down too aggressively.
Why wrong: Auto Scaling does not directly cause increased latency; it may cause minor disruption during scaling.
- B
The Aurora cluster volume uses a smaller buffer cache than the original RDS instance.
Why wrong: Aurora uses a shared storage volume; the buffer cache is on the instance, and if the instance class is the same, cache size is similar.
- C
The Aurora cluster is using the parallel query feature which adds overhead for complex queries.
Why wrong: Parallel query is designed to improve performance for analytical queries, not degrade it.
- D
The application is sending all read queries to the primary instance instead of offloading them to Aurora Replicas.
Without using Aurora Replicas, the primary handles all read traffic, leading to contention and higher latency.
Quick Answer
The answer is that the application is sending all read queries to the primary instance instead of offloading them to Aurora Replicas. This is the most likely cause of higher query latency after migrating to Aurora PostgreSQL because Aurora’s architecture separates storage from compute, and the primary instance must handle both writes and any reads directed at it. Even with low CPU, the primary can experience contention from competing write operations and buffer cache pressure, while Aurora Replicas are purpose-built to absorb read traffic from the shared cluster volume without impacting the writer. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of Aurora’s read scaling model and the common trap of assuming adequate instance size alone prevents latency. A frequent memory tip is to think of Aurora Replicas as “read-only helpers” that must be explicitly used by the application—if you don’t point read queries at them, you lose the main performance benefit of Aurora. Remember: low CPU does not mean no bottleneck; always check the read path first.
DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. 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 recently migrated their PostgreSQL database to Amazon Aurora PostgreSQL. They notice that the average query latency has increased, especially for complex read queries. The DB instance size is adequate and CPU utilization is below 50%. What is the MOST likely cause of the increased latency?
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 is sending all read queries to the primary instance instead of offloading them to Aurora Replicas.
Aurora PostgreSQL uses a shared cluster volume, and by default, writes are sent to the primary instance. Read replicas (Aurora Replicas) can offload read traffic. If the application is not using read replicas for read queries, all queries hit the primary, which may become overloaded even if CPU is low due to other bottlenecks like memory or I/O. However, the most typical cause for increased read latency after migration to Aurora is the lack of read replicas or incorrect query optimization. Option D (Aurora Replicas not used) is the most likely. Option A (buffer cache) is possible but less likely with adequate memory. Option B (Auto Scaling) doesn't cause increased latency. Option C (parallel query) is a feature that can improve performance, not degrade it.
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 policy for the Aurora cluster is set to scale down too aggressively.
Why it's wrong here
Auto Scaling does not directly cause increased latency; it may cause minor disruption during scaling.
- ✗
The Aurora cluster volume uses a smaller buffer cache than the original RDS instance.
Why it's wrong here
Aurora uses a shared storage volume; the buffer cache is on the instance, and if the instance class is the same, cache size is similar.
- ✗
The Aurora cluster is using the parallel query feature which adds overhead for complex queries.
Why it's wrong here
Parallel query is designed to improve performance for analytical queries, not degrade it.
- ✓
The application is sending all read queries to the primary instance instead of offloading them to Aurora Replicas.
Why this is correct
Without using Aurora Replicas, the primary handles all read traffic, leading to contention and higher latency.
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.
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
Similar concept trap
Aurora uses a shared storage volume; the buffer cache is on the instance, and if the instance class is the same, cache size is similar.
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 DBS-C01 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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Workload-Specific Database Design — study guide chapter
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The application is sending all read queries to the primary instance instead of offloading them to Aurora Replicas. — Aurora PostgreSQL uses a shared cluster volume, and by default, writes are sent to the primary instance. Read replicas (Aurora Replicas) can offload read traffic. If the application is not using read replicas for read queries, all queries hit the primary, which may become overloaded even if CPU is low due to other bottlenecks like memory or I/O. However, the most typical cause for increased read latency after migration to Aurora is the lack of read replicas or incorrect query optimization. Option D (Aurora Replicas not used) is the most likely. Option A (buffer cache) is possible but less likely with adequate memory. Option B (Auto Scaling) doesn't cause increased latency. Option C (parallel query) is a feature that can improve performance, not degrade it.
What should I do if I get this DBS-C01 question wrong?
Identify which DBS-C01 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
This DBS-C01 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 DBS-C01 exam.
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