The answer is to increase the instance size to a larger DB instance class. This vertical scaling solution directly reduces high write latency by provisioning more CPU and memory resources, which accelerates transaction processing and reduces I/O wait times for write operations. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of the trade-offs between vertical and horizontal scaling for RDS, with a common trap being the temptation to add read replicas—which only help read traffic, not write latency. The key insight is that write-heavy workloads benefit from a larger instance’s faster clock speed and larger buffer cache, not from distributing reads. For a memory tip, remember that “write latency” means you need more power in the single instance, not more copies: think “Vertical for Volume” when writes are the bottleneck.
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 production Amazon RDS for PostgreSQL database. The database experiences high write latency during peak hours. The company wants to reduce latency without changing the application code. Which solution is MOST cost-effective and scalable?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the instance size to a larger DB instance class
Increasing the instance size to a larger DB instance class directly addresses high write latency by providing more CPU and memory resources, which improves the database's ability to process write operations faster. This is the most cost-effective and scalable solution because it does not require application code changes and can be scaled vertically as needed, whereas other options either do not reduce write latency or introduce unnecessary complexity.
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.
✗
Change the storage type to Provisioned IOPS (io1)
Why it's wrong here
While io1 improves IOPS, it requires application changes to fully utilize; also cost may be higher.
✗
Enable RDS Proxy to pool database connections
Why it's wrong here
RDS Proxy reduces connection overhead, not write latency.
✓
Increase the instance size to a larger DB instance class
Why this is correct
Vertical scaling can improve write throughput.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a Multi-AZ standby to offload writes
Why it's wrong here
Multi-AZ standby does not offload writes; writes go to primary.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that Multi-AZ standby can offload writes, but in reality, the standby is a synchronous replica that does not accept write traffic and only provides failover redundancy.
Detailed technical explanation
How to think about this question
When a PostgreSQL instance experiences high write latency, it is often due to CPU exhaustion, memory pressure, or I/O wait caused by insufficient instance resources. Scaling up to a larger instance class (e.g., from db.r5.large to db.r5.xlarge) increases vCPUs and memory, allowing the database to handle more concurrent write transactions and reduce contention. This vertical scaling approach is straightforward and cost-effective for predictable workloads, whereas horizontal scaling (e.g., read replicas) would require application changes to direct read traffic away from the primary.
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.
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
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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Increase the instance size to a larger DB instance class — Increasing the instance size to a larger DB instance class directly addresses high write latency by providing more CPU and memory resources, which improves the database's ability to process write operations faster. This is the most cost-effective and scalable solution because it does not require application code changes and can be scaled vertically as needed, whereas other options either do not reduce write latency or introduce unnecessary complexity.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is running an Oracle database on Amazon RDS. The database has a large table that is frequently accessed by multiple applications. The DBA notices that the table has a high number of index scans but the queries are still slow. Upon investigation, the buffer cache hit ratio is low. Which design change would BEST improve performance?
hard
A.Convert the table to columnar storage using Amazon Redshift
B.Add a read replica to offload queries
C.Migrate the table to Amazon DynamoDB with DAX
✓ D.Increase the instance size to provide more memory
Why D: Option B is correct because increasing the instance size provides more memory for the buffer cache, improving cache hit ratio. Option A is wrong because read replicas do not help with buffer cache on the primary. Option C is wrong because converting to columnar is for analytical workloads. Option D is wrong because switching to DynamoDB would require application changes.
Last reviewed: Jun 30, 2026
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