SAA-C03 Design Resilient Architectures Practice Question
A ticket booking system runs on EC2 instances behind an Application Load Balancer. The design must tolerate the failure of one Availability Zone. What should the Auto Scaling group configuration include? The architecture review board prefers a managed AWS-native control.
⚠ Common exam trap
The trap here is that candidates might think a single large subnet or a Network Load Balancer provides AZ resilience, but subnets are AZ-scoped and an NLB is a separate load-balancing component, not an Auto Scaling group configuration setting.
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
✓
Subnets in at least two Availability Zones with health checks enabled
An Auto Scaling group configured with subnets in at least two Availability Zones ensures that if one AZ fails, the remaining AZ(s) can continue to serve traffic. Health checks on the EC2 instances allow the Auto Scaling group to detect and replace unhealthy instances, maintaining the desired capacity across the surviving AZs. This aligns with the requirement for a managed AWS-native control to tolerate an AZ failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Subnets in at least two Availability Zones with health checks enabled
Why this is correct
An Auto Scaling group spanning multiple AZs can replace unhealthy instances and maintain capacity during an AZ failure.
- ✗
All instances in one larger subnet
Why it's wrong here
One AZ remains a single point of failure.
- ✗
A Network Load Balancer in one subnet
Why it's wrong here
A load balancer in one AZ does not make the application resilient to AZ failure.
- ✗
A single EC2 instance with detailed monitoring
Why it's wrong here
Monitoring does not provide redundancy.
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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.