SAA-C03 Design Resilient Architectures Practice Question
This SAA-C03 practice question tests your understanding of design resilient architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: auto Scaling Groups can span multiple Availability Zones.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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 design must avoid adding custom operational scripts.
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
Option A is correct because placing subnets in at least two Availability Zones ensures that if one AZ fails, the Auto Scaling group can launch instances in the remaining healthy AZ, maintaining application availability. Health checks integrated with the Application Load Balancer allow the Auto Scaling group to automatically replace unhealthy instances without custom scripts, aligning with the requirement to avoid operational overhead.
Key principle: Auto Scaling Groups can span multiple Availability Zones.
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.
Related concept
Auto Scaling Groups can span multiple Availability Zones.
✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a single larger subnet or a Network Load Balancer provides AZ resilience, but they fail to recognize that without multiple subnets in distinct AZs, the architecture cannot survive an AZ failure, and custom scripts would be needed for health checks without ELB integration.
Detailed technical explanation
How to think about this question
Under the hood, the Auto Scaling group uses the EC2 health check (status checks) and the ELB health check (HTTP/HTTPS health checks) to determine instance health. When an instance fails an ELB health check, the Auto Scaling group marks it as unhealthy and terminates it, then launches a new instance in a different subnet (AZ) if the group spans multiple AZs. This design leverages the AWS Regional service model, where the Application Load Balancer is regional and can route traffic to targets in any AZ, ensuring fault isolation.
KKey Concepts to Remember
Auto Scaling Groups can span multiple Availability Zones.
Application Load Balancers distribute traffic across multiple Availability Zones.
Health checks are crucial for Auto Scaling Groups to identify and replace unhealthy instances.
Distributing resources across AZs protects against single AZ failures.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Auto Scaling Groups can span multiple Availability Zones.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Review auto Scaling Groups can span multiple Availability Zones., then practise related SAA-C03 questions on the same topic to reinforce the concept.
Design Resilient Architectures — This question tests Design Resilient Architectures — Auto Scaling Groups can span multiple Availability Zones..
What is the correct answer to this question?
The correct answer is: Subnets in at least two Availability Zones with health checks enabled — Option A is correct because placing subnets in at least two Availability Zones ensures that if one AZ fails, the Auto Scaling group can launch instances in the remaining healthy AZ, maintaining application availability. Health checks integrated with the Application Load Balancer allow the Auto Scaling group to automatically replace unhealthy instances without custom scripts, aligning with the requirement to avoid operational overhead.
What should I do if I get this SAA-C03 question wrong?
Review auto Scaling Groups can span multiple Availability Zones., then practise related SAA-C03 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Auto Scaling Groups can span multiple Availability Zones.
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Question Discussion
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