- A
Deploy a single EC2 instance in one Availability Zone with an Elastic IP address.
Why wrong: This design is not fault-tolerant; if the AZ fails, the application becomes unavailable.
- B
Use an Application Load Balancer in front of an Auto Scaling group spanning three Availability Zones.
ALB distributes traffic across multiple AZs and instances, providing fault tolerance and scalability.
- C
Deploy EC2 instances in a single Availability Zone and use Route 53 weighted routing.
Why wrong: A single AZ is a single point of failure; Route 53 weighted routing does not provide automatic failover.
- D
Use a Network Load Balancer with a single EC2 instance in each AZ.
Why wrong: NLB operates at layer 4 and does not support HTTP path-based routing; also, static instances do not provide elasticity.
How to Achieve High Availability and Horizontal Scaling with ALB and Auto Scaling Across Multiple AZs
This ANS-C01 practice question tests your understanding of network design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
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.
Option B is correct because 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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may 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.
Detailed technical explanation
How to think about this question
An Application Load Balancer operates at Layer 7 and can perform content-based routing, health checks, and offload SSL termination, which is ideal for web applications. The Auto Scaling group ensures that the number of EC2 instances adjusts based on demand, and by spanning three Availability Zones, it maintains capacity even if one AZ becomes impaired. Under the hood, the ALB uses a distributed node architecture across AZs, and each target group monitors instance health via HTTP/HTTPS health checks, automatically deregistering unhealthy targets.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an Application Load Balancer in front of an Auto Scaling group spanning three Availability Zones. — Option B is correct because 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.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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.
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