SAA-C03 Design Resilient Architectures Practice Question
A company runs a stateless API on Amazon EC2 instances in a single Availability Zone behind an Application Load Balancer. The ALB currently has a listener on port 80 only. The company wants the API to remain available if the single Availability Zone fails. What should the solutions architect do to meet this requirement with the LEAST operational overhead?
⚠ Common exam trap
The trap here is assuming that adding more instances inside the same Availability Zone or enabling cross-zone load balancing protects against a zone-level failure.
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 Amazon Machine Image (AMI) of the instances and configure an Auto Scaling group across at least two Availability Zones, registering the instances with the existing ALB target group.
Running the stateless API in an Auto Scaling group that spans at least two Availability Zones lets the group replace instances in a surviving zone when one zone becomes unavailable. The existing ALB and target group can be reused, so the change adds zone redundancy with the least operational overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable cross-zone load balancing on the ALB and increase the desired capacity of the existing instances in the single Availability Zone.
Why it's wrong here
Cross-zone load balancing only distributes traffic across registered targets in enabled zones. If all targets reside in one Availability Zone, a zone failure removes every target, so increasing capacity inside that same zone does not add resilience against a zone outage.
- ✗
Create a second ALB in another Availability Zone and use Amazon Route 53 failover routing with health checks to switch traffic when the primary zone fails.
Why it's wrong here
This adds a second load balancer and DNS failover logic, increasing cost and operational complexity. It also relies on DNS TTL and health-check timing for failover, which is slower and more manual than simply running an Auto Scaling group across multiple zones behind the existing ALB.
- ✓
Create an Amazon Machine Image (AMI) of the instances and configure an Auto Scaling group across at least two Availability Zones, registering the instances with the existing ALB target group.
Why this is correct
An Auto Scaling group spanning multiple Availability Zones automatically launches replacement instances in a healthy zone if one zone fails, and registers them with the existing target group. This provides zone-level resilience with minimal ongoing management because scaling and health replacement are handled by the service.
- ✗
Move the API to an Amazon S3 static website endpoint and serve the traffic through Amazon CloudFront with origin failover.
Why it's wrong here
Amazon S3 static website hosting serves static content only and cannot run the API's application logic. CloudFront origin failover helps with content delivery resilience but does not execute the compute layer, so this does not satisfy the requirement to keep the API running.
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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
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.