- A
Right-size the writer based on actual utilization instead of peak guesses.
Correct. Right-sizing removes waste from the always-on primary instance. If the writer is sized for real load rather than a worst-case assumption, the company pays for less unused compute.
- B
Add read replicas and direct dashboard traffic away from the writer.
Correct. Read replicas let read-heavy dashboards scale without forcing the writer to be oversized for every query. This improves scaling economics while keeping the application relational and largely unchanged.
- C
Evaluate Aurora MySQL if the current replica-heavy design would be cheaper there.
Correct. Aurora can be more cost-efficient than a replica-heavy RDS topology because storage is shared across the cluster and replicas are simpler to operate. It is a reasonable tradeoff to evaluate when read scaling is the main issue.
- D
Migrate to DynamoDB immediately because every relational workload is more expensive.
Why wrong: Incorrect. DynamoDB is not a drop-in replacement for a relational reporting app. A rewrite would be required, and the query pattern may not fit key-value access at all.
- E
Increase provisioned IOPS permanently so the monthly bill drops.
Why wrong: Incorrect. More provisioned IOPS increases cost, not decreases it. The issue is overprovisioned compute and topology, not a lack of enough disk performance everywhere.
SAA-C03 Design Cost-Optimized Architectures Practice Question
This SAA-C03 practice question tests your understanding of design cost-optimized architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: right-sizing involves matching instance types to actual usage patterns.. 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 retailer runs a reporting-heavy relational app on Amazon RDS MySQL. Peak dashboard traffic lasts only three hours each day, but the database is sized for the peak all day. The business wants lower cost without rewriting the application. Which three actions are best? Select three.
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Right-size the writer based on actual utilization instead of peak guesses.
Option A is correct because right-sizing the RDS instance based on actual utilization metrics (e.g., CPU, memory, connections) rather than peak guesses directly reduces compute and memory costs. Since the peak dashboard traffic lasts only three hours, the database can be scaled down for the remaining 21 hours, avoiding over-provisioning. This is a fundamental cost-optimization strategy for RDS without requiring application changes.
Key principle: Right-sizing involves matching instance types to actual usage patterns.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Right-size the writer based on actual utilization instead of peak guesses.
Why this is correct
Correct. Right-sizing removes waste from the always-on primary instance. If the writer is sized for real load rather than a worst-case assumption, the company pays for less unused compute.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Right-sizing involves matching instance types to actual usage patterns.
- ✓
Add read replicas and direct dashboard traffic away from the writer.
Why this is correct
Correct. Read replicas let read-heavy dashboards scale without forcing the writer to be oversized for every query. This improves scaling economics while keeping the application relational and largely unchanged.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Right-sizing involves matching instance types to actual usage patterns.
- ✓
Evaluate Aurora MySQL if the current replica-heavy design would be cheaper there.
Why this is correct
Correct. Aurora can be more cost-efficient than a replica-heavy RDS topology because storage is shared across the cluster and replicas are simpler to operate. It is a reasonable tradeoff to evaluate when read scaling is the main issue.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Right-sizing involves matching instance types to actual usage patterns.
- ✗
Migrate to DynamoDB immediately because every relational workload is more expensive.
Why it's wrong here
Incorrect. DynamoDB is not a drop-in replacement for a relational reporting app. A rewrite would be required, and the query pattern may not fit key-value access at all.
- ✗
Increase provisioned IOPS permanently so the monthly bill drops.
Why it's wrong here
Incorrect. More provisioned IOPS increases cost, not decreases it. The issue is overprovisioned compute and topology, not a lack of enough disk performance everywhere.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume DynamoDB is always cheaper for any workload, ignoring the need for application rewrites and the relational reporting requirements, while also overlooking that increasing IOPS always raises costs rather than lowering them.
Detailed technical explanation
How to think about this question
RDS right-sizing leverages CloudWatch metrics like `DatabaseConnections`, `CPUUtilization`, and `ReadIOPS` to select the optimal instance size (e.g., db.r5.large vs. db.r5.xlarge). For burstable instances like db.t3, CPU credits accumulate during idle periods, further reducing cost. Read replicas offload SELECT queries from the writer, but the writer still handles writes and DDL; Aurora MySQL can reduce storage costs by separating compute from storage and using a 6-replica quorum for durability.
KKey Concepts to Remember
- Right-sizing involves matching instance types to actual usage patterns.
- CloudWatch metrics (CPU, memory, connections) are crucial for right-sizing.
- Overprovisioning leads to unnecessary costs for idle resources.
- Right-sizing is a foundational step in AWS cost optimization.
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
Right-sizing involves matching instance types to actual usage patterns.
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
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Cost-Optimized Architectures — This question tests Design Cost-Optimized Architectures — Right-sizing involves matching instance types to actual usage patterns..
What is the correct answer to this question?
The correct answer is: Right-size the writer based on actual utilization instead of peak guesses. — Option A is correct because right-sizing the RDS instance based on actual utilization metrics (e.g., CPU, memory, connections) rather than peak guesses directly reduces compute and memory costs. Since the peak dashboard traffic lasts only three hours, the database can be scaled down for the remaining 21 hours, avoiding over-provisioning. This is a fundamental cost-optimization strategy for RDS without requiring application changes.
What should I do if I get this SAA-C03 question wrong?
Review right-sizing involves matching instance types to actual usage patterns., then practise related SAA-C03 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Right-sizing involves matching instance types to actual usage patterns.
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Last reviewed: Jun 11, 2026
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