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Question 820 of 1,040

Design Cost-Optimized Architectures →hardMultiple SelectObjective-mapped

Quick Answer

The answer is to evaluate Aurora MySQL if the current replica-heavy design would be cheaper there, right-size the RDS instance based on actual utilization, and consider using Aurora Auto Scaling with reader endpoints for the peak traffic window. This combination works because right-sizing eliminates paying for idle capacity during the 21 off-peak hours, while Aurora’s distributed storage and multi-AZ replica architecture often reduce I/O and storage costs compared to RDS MySQL for reporting-heavy workloads. On the SAA-C03 exam, this scenario tests your ability to optimize cost without application changes—a common trap is to suggest read replicas alone, which still incur full compute costs, or to propose rewriting queries. The key insight is that Aurora’s shared storage lets you scale read replicas independently and only pay for the compute during the three-hour peak. Memory tip: “Right-size, then Aurora-ize” to remember that sizing first, then evaluating Aurora’s replica economics, cuts peak traffic costs.

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. 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 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.

Question 1hardmulti select

Full question →

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.

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

✓

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) directly reduces cost by eliminating over-provisioning for the 3-hour peak. This is a fundamental cost-optimization practice that avoids paying for idle capacity during the remaining 21 hours.

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.

✓
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
Read the scenario before looking for a memorised answer.
✓
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
Read the scenario before looking for a memorised answer.
✓
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
Read the scenario before looking for a memorised answer.
✗
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 'sizing for peak' is always necessary, but AWS cost optimization emphasizes matching capacity to actual average utilization, not peak, and using services like read replicas or Aurora to handle spikes without over-provisioning the writer.

Detailed technical explanation

How to think about this question

RDS right-sizing involves analyzing CloudWatch metrics like DatabaseConnections, ReadIOPS, and CPUCreditBalance over a representative period (e.g., 14 days) to select the smallest instance type that meets the workload's sustained needs. For burstable instances like db.t3, CPU credits can handle short peaks, but sustained high usage requires a larger instance. This approach often reveals that a db.r5.large can replace a db.r5.xlarge, cutting costs by ~50%.

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.

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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 — Read the scenario before looking for a memorised answer..

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) directly reduces cost by eliminating over-provisioning for the 3-hour peak. This is a fundamental cost-optimization practice that avoids paying for idle capacity during the remaining 21 hours.

What should I do if I get this SAA-C03 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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?

Read the scenario before looking for a memorised answer.

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Same concept, more angles

1 more ways this is tested on SAA-C03

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 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.

hard

✓ A.Right-size the writer based on actual utilization instead of peak guesses.
✓ B.Add read replicas and direct dashboard traffic away from the writer.
✓ C.Evaluate Aurora MySQL if the current replica-heavy design would be cheaper there.
D.Migrate to DynamoDB immediately because every relational workload is more expensive.
E.Increase provisioned IOPS permanently so the monthly bill drops.

Why A: 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.

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Question Discussion

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