SAA-C03 Design Resilient Architectures Practice Question
A financial analytics platform runs a stateless API on Amazon EC2 instances in an Auto Scaling group behind a Network Load Balancer. The API reads from an Amazon Aurora MySQL cluster that has a single writer instance and one reader instance in a different Availability Zone. During a recent Availability Zone event, the writer instance failed and the API saw several minutes of failed writes. The team wants writes to resume automatically with minimal downtime and no application code changes. What should the solutions architect do?
⚠ Common exam trap
The trap here is reaching for manual promotion or multi-master when Aurora already performs automatic failover to a replica, provided the replica exists in a different Availability Zone.
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
✓
Ensure the Aurora cluster has at least one Aurora Replica in a different Availability Zone and rely on the cluster's automatic failover, which updates the writer endpoint to point at the promoted replica.
Aurora provides automatic failover by promoting an existing Aurora Replica to the writer role and updating the cluster writer endpoint, so applications that connect through that endpoint reconnect without modification. The prerequisite is that a replica exists in a different Availability Zone from the writer, which makes it a viable failover target when the writer's zone is lost.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Ensure the Aurora cluster has at least one Aurora Replica in a different Availability Zone and rely on the cluster's automatic failover, which updates the writer endpoint to point at the promoted replica.
Why this is correct
Aurora automatically promotes an Aurora Replica to writer when the current writer fails, and the cluster writer endpoint is repointed to the new writer, so the application keeps using the same endpoint and resumes writes without code changes. Having the replica in a separate Availability Zone ensures the failover target survives the zone event.
- ✗
Add a second Aurora reader instance in a third Availability Zone and update the application connection string to use the reader endpoint for all queries.
Why it's wrong here
Adding another reader improves read scalability and read availability, but it does not change the fact that a single writer instance remains the only endpoint accepting writes. Pointing the application at the reader endpoint would also break write operations, because reader endpoints reject writes, so this does not address the failover requirement.
- ✗
Create an Aurora Replica in a second Availability Zone and promote it manually to writer using the AWS Management Console when a failure occurs.
Why it's wrong here
Aurora already supports automatic failover to an existing replica, so a manual promotion process adds human latency and does not meet the minimal-downtime goal. Manual promotion also risks operator error during an incident and requires runbook execution, which conflicts with the requirement for automatic recovery without application changes.
- ✗
Convert the cluster to an Aurora multi-master cluster so every instance can accept writes, and keep the existing writer endpoint in the connection string.
Why it's wrong here
Aurora multi-master is designed for write scaling with conflict detection, not as a drop-in failover solution, and it is not supported for all Aurora MySQL versions or engines. It also changes write semantics and does not preserve the same behavior the application expects, so it is not the least-disruptive way to achieve automatic writer failover.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.