SAA-C03 Design Resilient Architectures Practice Question
A startup runs a stateless web application on a single Amazon EC2 instance in one Availability Zone. The application has become popular, and the startup wants to ensure that the application can survive the failure of an Availability Zone and can handle increased traffic. Which architecture change should the startup make FIRST?
⚠ Common exam trap
The trap here is focusing on vertical scaling or monitoring as a way to achieve high availability, when the real solution requires distributing the workload across multiple Availability Zones.
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
✓
Move the application to an Auto Scaling group that spans multiple Availability Zones, and place an Application Load Balancer in front of it.
Moving to an Auto Scaling group across multiple Availability Zones with an Application Load Balancer provides both high availability and elasticity. The load balancer health checks ensure traffic goes only to healthy instances, and the Auto Scaling group replaces failed instances automatically. This architecture eliminates single points of failure and allows the application to scale with demand, which is the fundamental first step for resilience.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Resize the existing EC2 instance to a larger instance type to handle increased traffic and improve availability.
Why it's wrong here
Vertical scaling increases capacity on a single instance but does not provide high availability. The instance remains in one Availability Zone, so an AZ failure still takes down the application. This approach also has a practical upper limit and requires downtime for resizing, so it does not meet the resilience requirement.
- ✗
Create an Amazon Machine Image (AMI) of the instance and store it in Amazon S3 for quick recovery after a failure.
Why it's wrong here
An AMI allows you to launch a new instance, but recovery is manual and not automatic. During an AZ failure, you would need to detect the failure and launch a replacement, causing downtime. This does not provide the continuous availability or scalability that the application needs as it grows.
- ✗
Enable detailed monitoring on the EC2 instance and create Amazon CloudWatch alarms to notify the team of failures.
Why it's wrong here
Monitoring and alarms improve visibility but do not automatically recover the application. The instance remains a single point of failure in one AZ, so an AZ outage still causes downtime. This option addresses detection, not resilience or scalability, and therefore does not meet the requirement.
- ✓
Move the application to an Auto Scaling group that spans multiple Availability Zones, and place an Application Load Balancer in front of it.
Why this is correct
An Auto Scaling group spanning multiple Availability Zones distributes instances across AZs, so the application survives an AZ failure. An Application Load Balancer distributes traffic and performs health checks, routing only to healthy instances. This provides both high availability and horizontal scalability, directly addressing the requirements with minimal changes.
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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
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