ANS-C01 Network Design Practice Question
A company is deploying a multi-tier web application across three Availability Zones in a single AWS Region. The web tier must be fault-tolerant and scale horizontally. Which network design provides the highest availability and scalability?
⚠ Common exam trap
Many exam-takers choose Option D thinking a Network Load Balancer is always better for performance, but they overlook that the question requires horizontal scalability and fault tolerance, which an ALB with Auto Scaling provides, whereas a static single-instance-per-AZ design cannot scale dynamically.
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
✓
Use an Application Load Balancer in front of an Auto Scaling group spanning three Availability Zones.
An Application Load Balancer (ALB) distributes incoming HTTP/HTTPS traffic across multiple targets, and when combined with an Auto Scaling group that spans three Availability Zones, it provides both horizontal scalability and fault tolerance. If one AZ fails, the ALB automatically routes traffic only to healthy instances in the remaining AZs, ensuring high availability. This design meets the requirement for a multi-tier web application that must scale horizontally and tolerate failures.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy a single EC2 instance in one Availability Zone with an Elastic IP address.
Why it's wrong here
This design is not fault-tolerant; if the AZ fails, the application becomes unavailable.
- ✓
Use an Application Load Balancer in front of an Auto Scaling group spanning three Availability Zones.
Why this is correct
ALB distributes traffic across multiple AZs and instances, providing fault tolerance and scalability.
- ✗
Deploy EC2 instances in a single Availability Zone and use Route 53 weighted routing.
Why it's wrong here
A single AZ is a single point of failure; Route 53 weighted routing does not provide automatic failover.
- ✗
Use a Network Load Balancer with a single EC2 instance in each AZ.
Why it's wrong here
NLB operates at layer 4 and does not support HTTP path-based routing; also, static instances do not provide elasticity.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 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 ANS-C01 exam.