SAA-C03 Design Resilient Architectures Practice Question
A claims workflow uses an RDS MySQL database and must remain available during an Availability Zone failure with minimal application changes. What should the architect enable? The design must avoid adding custom operational scripts.
⚠ Common exam trap
Test-takers frequently confuse read replicas with Multi-AZ deployments, assuming read replicas provide automatic failover, but they require manual promotion and do not maintain the same endpoint.
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 provides automatic failover to a standby replica in a different Availability Zone. This ensures high availability during an AZ failure with minimal application changes, as the DNS endpoint remains the same and failover is handled by AWS without custom scripts.
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) is designed to asynchronously copy objects from one S3 bucket in one Region to a bucket in another Region. It has no integration with RDS failover mechanics: RDS MySQL does not store its database files as S3 objects in a way that CRR would replicate, and CRR cannot detect an AZ outage or automatically promote a standby database. Even if you manually exported DB snapshots to S3 and replicated them, restoring would be a manual, time-consuming operation, not automatic high availability.
- ✓
Multi-AZ deployment for the RDS DB instance
Why this is correct
A Multi-AZ deployment is the correct RDS feature for availability because Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone within the same Region. The primary DB instance writes data synchronously to the standby before committing, and if the primary fails or its AZ becomes unavailable, RDS automatically performs failover to the standby by updating the DNS endpoint, typically within 60–120 seconds without requiring manual intervention. This eliminates the need for application-level failover logic and provides a clear improvement in availability for an RDS MySQL instance.
- ✗
EBS snapshots every hour
Why it's wrong here
Taking EBS snapshots every hour is a backup strategy, not a high-availability or automatic failover mechanism. For RDS, automated backups and manual snapshots are stored in S3 and can be used to restore to a point in time, but the restore process is manual and takes significant time, often involving launching a new DB instance. Even with hourly snapshots, you could lose up to an hour of changes, and the database would be unavailable for the entire duration of the restore, which fails to meet a requirement of 'remain 2 nines' or similar high-availability SLA.
- ✗
Read replicas only
Why it's wrong here
Read replicas alone do not provide automatic failover for the primary RDS instance. A read replica uses asynchronous replication, so it can lag behind the primary (often by seconds or more), and while you can manually promote a read replica to become a standalone primary, there is no built-in automatic detection of primary failure or automatic promotion. Read replicas are beneficial for offloading read traffic or for multi-region disaster recovery, but for automatic AZ-level failover of a single RDS MySQL database, you need Multi-AZ, not read replicas.
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Same concept, more angles
7 more ways this is tested on SAA-C03
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A claims workflow uses an RDS MySQL database and must remain available during an Availability Zone failure with minimal application changes. What should the architect enable? The team wants the control to be enforceable during normal operations.
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.EBS snapshots every hour
- D.Read replicas only
Why B: Multi-AZ deployment for RDS MySQL provides synchronous standby replication across two Availability Zones. In the event of an AZ failure, Amazon RDS automatically fails over to the standby in the other AZ, ensuring availability with minimal application changes (the same database endpoint is used). This meets the requirement for enforceability during normal operations because Multi-AZ is always active, not a manual or scheduled process.
Variation 2. A claims workflow uses an RDS MySQL database and must remain available during an Availability Zone failure with minimal application changes. What should the architect enable?
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.EBS snapshots every hour
- D.Read replicas only
Why B: 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 simply reconnects to the same endpoint). This meets the requirement for availability during an AZ outage without requiring code modifications.
Variation 3. A claims workflow uses an RDS MySQL database and must remain available during an Availability Zone failure with minimal application changes. What should the architect enable? The architecture review board prefers a managed AWS-native control.
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.EBS snapshots every hour
- D.Read replicas only
Why B: Multi-AZ deployment for RDS MySQL provides synchronous standby replication to a different Availability Zone. In the event of an AZ failure, RDS automatically fails over to the standby, ensuring high availability with minimal application changes (the same endpoint is used). This is a managed AWS-native solution that meets the architecture review board's preference.
Variation 4. 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? The team wants the control to be enforceable during normal operations.
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.Read replicas only
- D.EBS snapshots every hour
Why B: Multi-AZ deployment for RDS MySQL automatically provisions and synchronously replicates a standby instance 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 using the same endpoint). This meets the requirement of remaining available during an AZ failure while being enforceable during normal operations.
Variation 5. 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?
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.Read replicas only
- D.EBS snapshots every hour
Why B: 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.
Variation 6. 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? The architecture review board prefers a managed AWS-native control.
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.Read replicas only
- D.EBS snapshots every hour
Why B: Multi-AZ deployment for RDS MySQL provides synchronous standby replication to a different Availability Zone, ensuring automatic failover with zero data loss (RPO=0) and minimal downtime (RTO typically under 2 minutes) during an AZ failure. This is a managed AWS-native solution that requires no application changes beyond updating the connection string to use the CNAME endpoint.
Variation 7. 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? The design must avoid adding custom operational scripts.
medium- A.S3 Cross-Region Replication
- ✓ B.Multi-AZ deployment for the RDS DB instance
- C.Read replicas only
- D.EBS snapshots every hour
Why B: Multi-AZ deployment for RDS MySQL automatically provisions and maintains a synchronous standby replica in a different Availability Zone. If the primary AZ fails, RDS performs an automatic failover to the standby, ensuring database availability with minimal application changes (the application only needs to reconnect using the same endpoint). This meets the requirement of avoiding custom operational scripts.
JA
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.