SAA-C03 Design Secure Architectures Practice Question

An e-commerce application uses Aurora MySQL. Writes are modest, but the product-detail page generates many read-only queries and the writer instance CPU is high. The application can tolerate a small amount of replication lag on those reads. What should the team do?

⚠ Common exam trap

Candidates often confuse Multi-AZ (which only provides failover) with read replicas (which offload reads), leading candidates to pick Option D thinking it improves read performance.

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

✓

Add Aurora read replicas and send read-only traffic to the reader endpoint.

Adding Aurora read replicas and directing read-only traffic to the reader endpoint offloads SELECT queries from the writer instance, reducing its CPU load. Aurora replicas share the same underlying storage volume, so replication lag is minimal (typically <100ms) and acceptable for the product-detail page. This scales read throughput without increasing writer instance size or cost.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Add Aurora read replicas and send read-only traffic to the reader endpoint.
Why this is correct
Aurora read replicas are the right way to scale read-heavy workloads and reduce pressure on the writer instance. By directing read-only traffic to the reader endpoint, the application can offload product-page queries while keeping writes on the primary instance. Because a small amount of replication lag is acceptable, this approach aligns well with the workload's consistency and performance needs.
✗
Increase the writer instance size and keep all traffic on the primary.
Why it's wrong here
A larger writer may temporarily relieve CPU pressure, but it does not solve the architectural issue of read traffic competing with writes. The application would still send every query to the primary instance, limiting future scalability. Since the reads can tolerate a bit of lag, offloading them to replicas is a better design.
When this WOULD be correct
If the application cannot tolerate any replication lag and all queries must be strongly consistent, or if the read workload is already low and the bottleneck is write performance, then increasing the writer instance size would be correct.
✗
Replace Aurora with DynamoDB to eliminate replication lag.
Why it's wrong here
Switching database engines would require major application redesign and is not the simplest answer to a read-scaling problem in Aurora. DynamoDB has different query patterns, data modeling rules, and consistency behavior. The question asks how to improve the current Aurora architecture, so a full migration is unnecessary and too disruptive.
When this WOULD be correct
A question where the application requires a fully managed NoSQL database with single-digit millisecond latency at any scale, and the data model is key-value or document-based, with no need for complex joins or transactions. For example: 'A gaming leaderboard needs to store player scores and retrieve top players with low latency; the data is simple and does not require relational queries.'
✗
Enable Multi-AZ failover only, because it increases read throughput automatically.
Why it's wrong here
Multi-AZ improves availability and failover behavior, but it is not a read-scaling feature. It ensures that the database can recover quickly if the primary fails, yet it does not automatically redirect large volumes of read traffic away from the writer for performance purposes. The problem here is read load, not just availability.
When this WOULD be correct
A question where the primary concern is database availability during an AZ outage, and read scaling is not required. For example: 'An application needs automatic failover to a standby instance in another AZ with zero data loss. What should be enabled?'

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.

✓Add Aurora read replicas and send read-only traffic to the reader endpoint.Correct answer▾

Why this is correct

Aurora read replicas are the right way to scale read-heavy workloads and reduce pressure on the writer instance. By directing read-only traffic to the reader endpoint, the application can offload product-page queries while keeping writes on the primary instance. Because a small amount of replication lag is acceptable, this approach aligns well with the workload's consistency and performance needs.

✗Increase the writer instance size and keep all traffic on the primary.Wrong answer — click to see why▾

Why this is wrong here

Increasing the writer instance size does not offload read traffic from the primary node, so CPU remains high from read queries. The question explicitly allows replication lag, making read replicas a more cost-effective and scalable solution.

★ When this WOULD be the correct answer

If the application cannot tolerate any replication lag and all queries must be strongly consistent, or if the read workload is already low and the bottleneck is write performance, then increasing the writer instance size would be correct.

Why candidates choose this

Candidates may think that a larger instance handles more throughput overall, overlooking that read replicas can distribute read load without scaling the writer.

✗Replace Aurora with DynamoDB to eliminate replication lag.Wrong answer — click to see why▾

Why this is wrong here

DynamoDB is a NoSQL database that does not support the same relational query patterns as Aurora MySQL, and the application would require significant refactoring. Additionally, DynamoDB does not inherently eliminate replication lag; it uses eventually consistent reads by default, which can have lag.

★ When this WOULD be the correct answer

A question where the application requires a fully managed NoSQL database with single-digit millisecond latency at any scale, and the data model is key-value or document-based, with no need for complex joins or transactions. For example: 'A gaming leaderboard needs to store player scores and retrieve top players with low latency; the data is simple and does not require relational queries.'

Why candidates choose this

Candidates may think DynamoDB is always faster and has no replication lag, overlooking the fact that it uses eventually consistent reads and requires application changes to adapt to a different data model.

✗Enable Multi-AZ failover only, because it increases read throughput automatically.Wrong answer — click to see why▾

Why this is wrong here

Multi-AZ failover provides high availability but does not increase read throughput; the standby replica cannot serve reads, so it does not offload the writer instance's CPU.

★ When this WOULD be the correct answer

A question where the primary concern is database availability during an AZ outage, and read scaling is not required. For example: 'An application needs automatic failover to a standby instance in another AZ with zero data loss. What should be enabled?'

Why candidates choose this

Candidates may confuse Multi-AZ with read replicas, thinking the standby can handle read traffic, or assume that failover automatically improves performance.

Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

Go deeper

SAA-C03 Design Secure Architectures Practice Question

Why each option matters

Option-by-option breakdown

Why each answer is right or wrong

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