SAA-C03 Design Resilient Architectures Practice Question
A financial services firm runs a critical API on Amazon EC2 instances behind a Network Load Balancer. The API must handle a sudden loss of one Availability Zone and continue serving traffic with no manual failover. The instances are in an Auto Scaling group that currently uses a single subnet in one Availability Zone. Which change should the architect make?
⚠ Common exam trap
The trap here is believing that cross-zone load balancing or a larger desired capacity creates Availability Zone redundancy, when both still depend on having subnets and instances in more than one AZ.
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
✓
Recreate the Auto Scaling group with subnets in at least two Availability Zones, enable the Network Load Balancer across those subnets, and attach a target group with health checks.
The Network Load Balancer must be enabled in subnets across multiple Availability Zones, and the Auto Scaling group must launch instances in those same subnets. With health checks on the target group, failed instances and the failed AZ are removed from rotation automatically, so the API remains available without manual failover.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace the Network Load Balancer with an Application Load Balancer and enable sticky sessions with a long cookie duration.
Why it's wrong here
Changing the load balancer type does not add Availability Zone redundancy if the Auto Scaling group still uses one subnet. Sticky sessions can actually reduce resilience by pinning clients to instances that may fail, and the scenario does not require HTTP-level routing features, so this change does not solve the AZ failure requirement.
- ✗
Create an Amazon Route 53 latency-based routing record that points to the Network Load Balancer and set a failover routing policy with a health check.
Why it's wrong here
Route 53 failover routing requires a secondary endpoint in another Region or another load balancer. With only one Network Load Balancer in one Availability Zone, there is no healthy secondary target, so DNS failover cannot restore service when that AZ fails.
- ✗
Enable cross-zone load balancing on the Network Load Balancer and increase the Auto Scaling group desired capacity to four instances in the existing subnet.
Why it's wrong here
Cross-zone load balancing distributes traffic across registered targets in enabled AZs, but with only one subnet and one AZ, there are no other AZs to balance across. Increasing desired capacity in the same subnet still leaves all instances in a single failure domain, so an AZ loss takes down the entire API.
- ✓
Recreate the Auto Scaling group with subnets in at least two Availability Zones, enable the Network Load Balancer across those subnets, and attach a target group with health checks.
Why this is correct
A Network Load Balancer requires subnets in each Availability Zone where it should accept traffic, and an Auto Scaling group spanning multiple AZs keeps instances running if one AZ fails. Health checks remove failed targets, so the API continues serving with no manual intervention, which is exactly the resilience the firm needs.
Visual reference
Go deeper
Related to this question
About these practice questions
This SAA-C03 question is part of Courseiva's 935-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.