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 distribute instances across specified subnets.. 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 team wants the control to be enforceable during normal operations.
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 distributing subnets across at least two Availability Zones ensures that if one AZ fails, the Auto Scaling group can launch replacement instances in the remaining AZ(s) to maintain capacity. Enabling health checks on the Application Load Balancer allows the Auto Scaling group to detect and replace unhealthy instances, enforcing resilience during normal operations without manual intervention.
Key principle: Auto Scaling Groups distribute instances across specified subnets.
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 distribute instances across specified subnets.
✗
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 high availability, but they overlook the requirement for multi-AZ distribution and application-layer health checks to enforce resilience during normal operations.
Detailed technical explanation
How to think about this question
Under the hood, the Auto Scaling group uses the health check grace period (default 300 seconds) to allow an instance to stabilize before marking it unhealthy. The ALB health checks target specific paths (e.g., /health) with configurable intervals (default 30 seconds) and thresholds (e.g., 2 consecutive failures to mark unhealthy). In a real-world scenario, if the ALB health check fails for an instance in AZ-a, the Auto Scaling group terminates it and launches a new one in AZ-b, provided the group spans at least two AZs.
KKey Concepts to Remember
Auto Scaling Groups distribute instances across specified subnets.
Application Load Balancers are regional and distribute traffic across multiple AZs.
Health checks enable ASGs to replace unhealthy instances.
Multi-AZ deployment protects against Availability Zone 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 distribute instances across specified subnets.
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 distribute instances across specified subnets., 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 distribute instances across specified subnets..
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 distributing subnets across at least two Availability Zones ensures that if one AZ fails, the Auto Scaling group can launch replacement instances in the remaining AZ(s) to maintain capacity. Enabling health checks on the Application Load Balancer allows the Auto Scaling group to detect and replace unhealthy instances, enforcing resilience during normal operations without manual intervention.
What should I do if I get this SAA-C03 question wrong?
Review auto Scaling Groups distribute instances across specified subnets., 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 distribute instances across specified subnets.
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Question Discussion
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