Quick Answer
The correct answer is the combination of an Application Load Balancer (ALB), a NAT Gateway, and an Auto Scaling group with instances in multiple Availability Zones. The ALB provides cross-zone load balancing, distributing traffic across healthy targets in any AZ, which eliminates a single point of failure at the traffic distribution layer. The NAT Gateway, deployed in each AZ, ensures outbound internet traffic remains available even if one AZ fails, while the Auto Scaling group automatically replaces failed instances across AZs to maintain capacity. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this triad tests your understanding of how to architect for fault tolerance at the network, compute, and egress layers—a common trap is forgetting that NAT Gateways are AZ-specific and require one per AZ for true high availability. A useful memory tip is "ALB for in, NAT for out, Auto Scaling for about"—covering traffic ingress, egress, and instance resilience.
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 designing a high-availability architecture for an application that will be deployed across multiple Availability Zones. Which THREE components are recommended for this design? (Choose three.)
One EC2 instance in each AZ
Why wrong: No auto-healing, manual failure handling.
Application Load Balancer across multiple AZs
Distributes traffic across AZs.
NAT Gateway in each AZ
Provides HA for outbound internet access.
Auto Scaling group with instances in multiple AZs
Automatically maintains instance health across AZs.
Single NAT Gateway in one AZ
Why wrong: Single point of failure.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Application Load Balancer across multiple AZs
An Application Load Balancer (ALB) distributes incoming traffic across multiple targets in different Availability Zones (AZs). By enabling cross-zone load balancing, the ALB can route requests to healthy instances in any AZ, ensuring that if one AZ fails, traffic is automatically redirected to instances in the remaining AZs. This is a foundational component for high availability because it eliminates a single point of failure at the traffic distribution layer.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
One EC2 instance in each AZ
Why it's wrong here
No auto-healing, manual failure handling.
Application Load Balancer across multiple AZs
Why this is correct
Distributes traffic across AZs.
Related concept
Read the scenario before looking for a memorised answer.
NAT Gateway in each AZ
Why this is correct
Provides HA for outbound internet access.
Related concept
Read the scenario before looking for a memorised answer.
Auto Scaling group with instances in multiple AZs
Why this is correct
Automatically maintains instance health across AZs.
Related concept
Read the scenario before looking for a memorised answer.
Single NAT Gateway in one AZ
Why it's wrong here
Single point of failure.
Common exam traps
AWS often tests the misconception that a single NAT Gateway is sufficient for high availability, but in a multi-AZ architecture, you must deploy a NAT Gateway in each AZ to maintain outbound connectivity during an AZ failure.
Detailed technical explanation
Under the hood, an ALB uses a shared IP address per AZ and performs health checks on targets via HTTP/HTTPS or TCP probes. When cross-zone load balancing is enabled, the ALB distributes traffic evenly across all registered instances regardless of AZ, which can mask uneven instance counts but also increases inter-AZ data transfer costs. In a real-world scenario, pairing an ALB with an Auto Scaling group that maintains a minimum number of instances per AZ ensures that even during a full AZ outage, the remaining AZs can handle the load without manual intervention.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
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FAQ
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
The correct answer is: Application Load Balancer across multiple AZs — An Application Load Balancer (ALB) distributes incoming traffic across multiple targets in different Availability Zones (AZs). By enabling cross-zone load balancing, the ALB can route requests to healthy instances in any AZ, ensuring that if one AZ fails, traffic is automatically redirected to instances in the remaining AZs. This is a foundational component for high availability because it eliminates a single point of failure at the traffic distribution layer.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a VPC architecture for a web application that must be highly available across multiple Availability Zones. Which TWO components should be deployed in at least two Availability Zones to meet this requirement?
easyWhy C: Options B and D are correct. NAT Gateways are AZ-specific, so deploying in multiple AZs ensures availability if one AZ fails. Application Load Balancers are regional services but can be configured with subnets in multiple AZs. Option A is wrong because an Internet Gateway is a horizontally scaled, redundant service per VPC, not per AZ. Option C is wrong because a VPN connection is per VPC, not per AZ. Option E is wrong because a Transit Gateway is a regional service.
Variation 2. A company is designing a network architecture for a critical application that requires high availability and fault tolerance. The application will be deployed on EC2 instances in an Auto Scaling group across three Availability Zones. The instances must be able to communicate with each other across AZs. Which TWO design decisions improve the fault tolerance of the application? (Choose TWO.)
mediumWhy C: Options B and D are correct. Option B is correct because distributing instances across three AZs ensures that the application survives an AZ failure. Option D is correct because Auto Scaling across AZs automatically replaces failed instances. Option A is wrong because a single NAT Gateway is a single point of failure. Option C is wrong because a single NLB in one AZ is a single point of failure. Option E is wrong because VPC endpoints do not improve fault tolerance for inter-instance communication.
Last reviewed: Jun 30, 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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