The answer is to change the application so that read-only queries are sent to the Aurora reader endpoint. This is correct because the reader endpoint automatically distributes read traffic across all available Aurora replicas, directly increasing read throughput while offloading the writer instance that is nearing its CPU limits. Since the reader instance in the scenario is idle, this single configuration change immediately reduces writer CPU pressure without requiring any database scaling or architectural redesign. On the SAA-C03 exam, this question tests your understanding of Aurora’s distinct endpoints: the writer endpoint handles both reads and writes, but the reader endpoint is optimized for read-heavy workloads and load balancing. A common trap is assuming you need to add more reader instances first, but the real bottleneck is misrouted traffic, not capacity. Memory tip: think of the reader endpoint as a “read-only traffic cop” that directs queries away from the writer, keeping the writer free for writes.
SAA-C03 Design High-Performing Architectures Practice Question
This SAA-C03 practice question tests your understanding of design high-performing 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.
Exhibit
Aurora cluster configuration:
- 1 writer instance
- 1 reader instance
- Application JDBC string: jdbc:mysql://cluster-writer.endpoint.example.com:3306/orders
CloudWatch metrics (peak hour):
- DBWriterCPUUtilization: 84%
- DBReaderCPUUtilization: 17%
- DatabaseConnections: steady
- ReadLatency p95: 38 ms
- WriteLatency p95: 9 ms
Application trace sample:
SELECT order_id, status, total FROM orders WHERE customer_id=? ORDER BY created_at DESC LIMIT 20
Based on the exhibit, an Amazon Aurora MySQL application is read-heavy, but the database writer is nearing CPU limits while the reader instance is mostly idle. The application currently sends all queries to the writer endpoint. Which change should you make first to increase read throughput?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Aurora cluster configuration:
- 1 writer instance
- 1 reader instance
- Application JDBC string: jdbc:mysql://cluster-writer.endpoint.example.com:3306/orders
CloudWatch metrics (peak hour):
- DBWriterCPUUtilization: 84%
- DBReaderCPUUtilization: 17%
- DatabaseConnections: steady
- ReadLatency p95: 38 ms
- WriteLatency p95: 9 ms
Application trace sample:
SELECT order_id, status, total FROM orders WHERE customer_id=? ORDER BY created_at DESC LIMIT 20
A
Keep using the writer endpoint so Aurora can route the reads automatically.
Why wrong: The writer endpoint sends traffic to the writer instance, which is already the bottleneck. It does not offload read traffic to the idle reader and therefore does not improve throughput.
B
Change the application to send read-only queries to the Aurora reader endpoint.
The reader endpoint is designed to distribute read traffic across Aurora replica instances. Moving SELECT-heavy traffic off the writer immediately reduces writer CPU pressure and increases total read throughput.
C
Convert the cluster to a single-AZ deployment so network hops are reduced.
Why wrong: Aurora is already a managed multi-AZ service, and reducing AZ diversity would hurt resilience without solving the read bottleneck. The problem is query routing, not inter-AZ overhead.
D
Add an Amazon DynamoDB Accelerator (DAX) cluster in front of Aurora.
Why wrong: DAX is for DynamoDB, not Aurora MySQL. It cannot accelerate SQL reads from Aurora or change how the application routes database queries.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the application to send read-only queries to the Aurora reader endpoint.
The correct answer is B because the Aurora reader endpoint is specifically designed to distribute read-only traffic across all available reader instances, offloading the writer and increasing read throughput. Since the reader instance is idle, directing read queries to the reader endpoint immediately reduces CPU load on the writer without requiring any architectural changes.
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.
✗
Keep using the writer endpoint so Aurora can route the reads automatically.
Why it's wrong here
The writer endpoint sends traffic to the writer instance, which is already the bottleneck. It does not offload read traffic to the idle reader and therefore does not improve throughput.
✓
Change the application to send read-only queries to the Aurora reader endpoint.
Why this is correct
The reader endpoint is designed to distribute read traffic across Aurora replica instances. Moving SELECT-heavy traffic off the writer immediately reduces writer CPU pressure and increases total read throughput.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Convert the cluster to a single-AZ deployment so network hops are reduced.
Why it's wrong here
Aurora is already a managed multi-AZ service, and reducing AZ diversity would hurt resilience without solving the read bottleneck. The problem is query routing, not inter-AZ overhead.
✗
Add an Amazon DynamoDB Accelerator (DAX) cluster in front of Aurora.
Why it's wrong here
DAX is for DynamoDB, not Aurora MySQL. It cannot accelerate SQL reads from Aurora or change how the application routes database queries.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the writer endpoint automatically load-balances reads across all instances, but in Aurora the writer endpoint always points to the primary instance, and only the reader endpoint distributes read traffic.
Detailed technical explanation
How to think about this question
Aurora reader endpoints use a load-balanced DNS name that connects to all available reader instances in the cluster, allowing horizontal scaling of read traffic. Under the hood, Aurora uses a shared storage volume, so reader instances can serve reads with minimal latency without requiring data replication, making the reader endpoint highly efficient for read-heavy workloads. In real-world scenarios, failing to use the reader endpoint is a common cause of writer CPU saturation even when reader capacity is available.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
Design High-Performing Architectures — This question tests Design High-Performing Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change the application to send read-only queries to the Aurora reader endpoint. — The correct answer is B because the Aurora reader endpoint is specifically designed to distribute read-only traffic across all available reader instances, offloading the writer and increasing read throughput. Since the reader instance is idle, directing read queries to the reader endpoint immediately reduces CPU load on the writer without requiring any architectural changes.
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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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