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 is running a MySQL database on Amazon RDS for a customer relationship management (CRM) application. The database has a table named 'contacts' with over 100 million rows. The application frequently runs queries to find contacts by email address. The email column has a B-tree index. Recently, the application started experiencing slow query performance. The team checked CloudWatch metrics and saw that the ReadIOPS for the RDS instance is consistently at 80% of the provisioned IOPS limit. The instance type is db.r5.large with 3000 provisioned IOPS (gp2). The buffer pool hit ratio is 95%. What is the most cost-effective design change to improve query performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Upgrade the RDS instance to db.r5.xlarge with 6000 provisioned IOPS.
Option B is correct because moving to a db.r5.xlarge with 6000 provisioned IOPS (gp2) doubles IOPS capacity, reducing IO wait. Option A is wrong because DynamoDB requires application changes. Option C is wrong because Elasticsearch is additional complexity and cost. Option D is wrong because the buffer pool hit ratio is already high; increasing memory won't help much.
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.
✓
Upgrade the RDS instance to db.r5.xlarge with 6000 provisioned IOPS.
Why this is correct
Increases IOPS capacity, reducing IO bottleneck.
Related concept
Read the scenario before looking for a memorised answer.
✗
Migrate the contacts table to Amazon DynamoDB with email as partition key.
Why it's wrong here
Requires significant application changes.
✗
Implement an Amazon OpenSearch Service cluster for email search.
Why it's wrong here
Adds complexity and cost; not cost-effective.
✗
Increase the buffer pool size by changing to a memory-optimized instance.
Why it's wrong here
Buffer pool hit ratio is already high; more memory yields diminishing returns.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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.
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: Upgrade the RDS instance to db.r5.xlarge with 6000 provisioned IOPS. — Option B is correct because moving to a db.r5.xlarge with 6000 provisioned IOPS (gp2) doubles IOPS capacity, reducing IO wait. Option A is wrong because DynamoDB requires application changes. Option C is wrong because Elasticsearch is additional complexity and cost. Option D is wrong because the buffer pool hit ratio is already high; increasing memory won't help much.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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