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 must remain available if the instance fails or if its Availability Zone becomes unavailable. The startup wants a managed solution that requires minimal operational overhead. Which solution should a solutions architect recommend?
⚠ Common exam trap
The trap here is believing that a single-zone Auto Scaling group provides Availability Zone resilience, when it can only replace instances within the same zone.
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
✓
Create an Auto Scaling group spanning at least two Availability Zones and attach it to an Application Load Balancer.
An Auto Scaling group that spans at least two Availability Zones can replace a failed instance and can also launch instances in a healthy zone when one zone becomes unavailable. Attaching an Application Load Balancer provides a stable endpoint and health-based routing, delivering a managed, resilient architecture with minimal operational effort.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Launch a second EC2 instance in the same Availability Zone and configure an Elastic IP address for failover.
Why it's wrong here
Placing a second instance in the same Availability Zone does not protect against a zone-level failure, because both instances become unavailable together. Elastic IP address reassignment is also a manual process that increases recovery time. This approach adds cost without satisfying the requirement to survive an Availability Zone failure.
- ✓
Create an Auto Scaling group spanning at least two Availability Zones and attach it to an Application Load Balancer.
Why this is correct
An Auto Scaling group spanning multiple Availability Zones automatically replaces failed instances and can launch replacements in healthy zones when one zone fails. Attaching an Application Load Balancer distributes traffic across healthy instances and provides a single stable endpoint. This is a managed, low-overhead solution that meets both instance and zone failure requirements.
- ✗
Migrate the application to AWS Lambda and expose it through an API Gateway REST API.
Why it's wrong here
AWS Lambda and API Gateway are highly available and managed, but migrating a web application to a serverless model is a significant re-architecture, not a minimal-overhead change. The scenario describes a stateless web application that can remain on EC2. This option introduces unnecessary redesign effort and does not directly address the stated requirement.
- ✗
Create an Auto Scaling group with a desired capacity of one instance and place it in a single Availability Zone.
Why it's wrong here
An Auto Scaling group in a single Availability Zone can replace a failed instance, but it cannot launch a replacement in another zone if the entire zone becomes unavailable. The scenario explicitly requires resilience to an Availability Zone failure, so this configuration does not meet the requirement. It also provides no benefit over the current single-instance setup for zone-level failures.
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JA
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.