SAA-C03 Design Resilient Architectures Practice Question
A team runs an Amazon RDS for MySQL database in a single Availability Zone. They want automatic failover with minimal downtime if the primary database instance becomes unavailable. Automated backups are already enabled. Which configuration change best meets the requirement?
⚠ Common exam trap
Watch out — candidates often confuse read replicas (which are for read scaling and manual promotion) with Multi-AZ (which is for high availability and automatic failover), leading them to incorrectly choose Option B.
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
✓
Enable RDS Multi-AZ so AWS maintains a standby in another Availability Zone for automatic failover.
Enabling Multi-AZ on Amazon RDS for MySQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary instance fails, Amazon RDS automatically fails over to the standby, typically within 60–120 seconds, minimizing downtime without manual intervention. This meets the requirement for automatic failover with minimal downtime.
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 the deployment as single-AZ, but increase automated backup retention to 35 days.
Why it's wrong here
Increasing automated backup retention from the default to 35 days only extends the window for point-in-time recovery and allows you to restore a historical database state. It does nothing to create a second, synchronized instance in another Availability Zone — no standby exists to take over if the primary fails. Because RDS remains single-AZ, an AZ outage or instance failure will still cause downtime until a manual restore or restart completes, so this does not satisfy the requirement for automatic failover.
- ✗
Create a read replica in another Availability Zone, but keep Multi-AZ disabled.
Why it's wrong here
A read replica provides additional read capacity and offloading, but it is not the same as the managed Multi-AZ synchronous standby used for automatic failover. Read replicas generally do not provide the same automated promotion behavior for the primary endpoint during an AZ outage.
- ✓
Enable RDS Multi-AZ so AWS maintains a standby in another Availability Zone for automatic failover.
Why this is correct
RDS Multi-AZ creates a standby instance in a different AZ and replicates data to it. If the primary becomes unavailable, AWS performs an automatic failover, promoting the standby and maintaining high availability with minimal application disruption.
- ✗
Rely on restoring from the most recent manual snapshot after an outage.
Why it's wrong here
Restoring from a manual snapshot after an outage is a manual recovery procedure, not an automatic one. It requires you to notice the failure, initiate a restore operation that typically provisions a new DB instance, and then wait for the restore to complete — minutes to hours depending on database size. Moreover, a snapshot only captures a point in time, so any transactions committed after the snapshot was taken are lost, unlike Multi-AZ's synchronous replication that maintains a fully current standby for automatic failover.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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