SAA-C03 Design Resilient Architectures Practice Question
A payments API uses an RDS MySQL database and must remain available during an Availability Zone failure with minimal application changes. What should the architect enable?
⚠ Common exam trap
Many candidates confuse read replicas (which are for read scaling and manual promotion) with Multi-AZ (which provides automatic failover for high availability), leading them to select read replicas as a cheaper or simpler alternative.
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
✓
Multi-AZ deployment for the RDS DB instance
Multi-AZ deployment for RDS MySQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. In the event of an AZ failure, Amazon RDS automatically fails over to the standby, providing high availability with minimal application changes (the application only needs to reconnect to the same endpoint). This meets the requirement for availability during an AZ outage without requiring code modifications.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
S3 Cross-Region Replication
Why it's wrong here
S3 Cross-Region Replication (CRR) automatically replicates objects between S3 buckets in different AWS Regions. It is designed for bucket-level object replication, not for database instances. RDS MySQL does not use S3 CRR for high availability or failover; any use of S3 would only be for backups or manual export/import, which cannot provide automatic database failover.
- ✓
Multi-AZ deployment for the RDS DB instance
Why this is correct
A Multi-AZ deployment creates a synchronized standby replica in a different Availability Zone of the same Region. Amazon RDS automatically fails over to the standby when a problem is detected on the primary, providing high availability for the DB instance. This is the correct solution for automatic, synchronous failover with minimal data loss.
- ✗
Read replicas only
Why it's wrong here
Read replicas are independent MySQL instances that asynchronously replicate from the primary to offload read traffic; they are not designed for automatic failover. While a read replica can be promoted to a primary role manually during a disaster, that action is not automatic and may lose recent transactions due to asynchronous lag. For automatic high availability, you need Multi-AZ, not just read replicas.
- ✗
EBS snapshots every hour
Why it's wrong here
Taking EBS snapshots every hour provides point-in-time recovery for the underlying storage, but restoring a snapshot creates a new database instance from that backup. This is a manual recovery process that involves downtime; it does not provide automatic failover or continuous availability. Snapshots protect data durability but are not a high-availability feature.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.