SAA-C03 Design Resilient Architectures Practice Question
A company runs a critical two-tier web application on AWS. The web tier consists of Amazon EC2 instances behind an Application Load Balancer (ALB) in a single Availability Zone. The database tier is an Amazon RDS for MySQL DB instance in the same Availability Zone. A recent power outage in that Availability Zone caused a full application outage. The company wants to redesign the architecture to survive an Availability Zone failure with minimal operational overhead. Which solution meets these requirements?
⚠ Common exam trap
The trap here is assuming that enabling Multi-AZ on RDS alone provides full application resilience while ignoring the single-AZ web tier.
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
✓
Deploy the web tier across two Availability Zones with an ALB, and convert the database to an RDS Multi-AZ DB instance.
The correct design distributes the stateless web tier across multiple Availability Zones and uses an RDS Multi-AZ DB instance for automatic database failover. This eliminates single points of failure at both tiers and requires little ongoing operational effort. Other options either leave the web tier in one AZ or rely on manual recovery for the database, failing the resilience and minimal-overhead goals.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use an Application Load Balancer with cross-zone load balancing enabled and enable Multi-AZ on the RDS instance.
Why it's wrong here
Cross-zone load balancing only distributes traffic across registered targets in multiple AZs; it does not create targets in another AZ if none exist. The EC2 instances remain in one AZ, so an AZ failure still takes down the web tier. While RDS Multi-AZ helps the database, the overall architecture remains vulnerable.
- ✗
Enable RDS automated backups with a 30-day retention period and create a read replica in a second Availability Zone.
Why it's wrong here
Automated backups and a read replica do not provide automatic failover for the primary DB instance. A read replica is asynchronous and requires manual promotion, which increases recovery time and operational effort. The web tier would still be confined to a single AZ, so an AZ failure would still cause an outage. This does not meet the minimal-overhead, resilient requirement.
- ✗
Place the EC2 instances in an Auto Scaling group spanning two Availability Zones, and take nightly snapshots of the RDS instance to restore in the second AZ.
Why it's wrong here
Auto Scaling across two AZs improves web tier resilience, but nightly snapshots require manual restoration and result in significant data loss and downtime. This approach does not provide automatic database failover and introduces substantial operational overhead. The requirement for minimal operational overhead and survival of an AZ failure is not satisfied.
- ✓
Deploy the web tier across two Availability Zones with an ALB, and convert the database to an RDS Multi-AZ DB instance.
Why this is correct
Spreading EC2 instances across two AZs behind an ALB removes the single point of failure for the web tier, and an RDS Multi-AZ DB instance maintains a synchronous standby in a different AZ. On failure, RDS automatically fails over to the standby, and the ALB routes traffic to healthy instances. This design survives an AZ outage with minimal operational overhead.
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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.