- A
Place web servers in public subnets across three AZs. Place application and database servers in private subnets across three AZs. Use a NAT Gateway in each AZ for outbound traffic.
Highly available and cost-effective managed service.
- B
Place web servers in public subnets across three AZs. Place application and database servers in private subnets across three AZs. Use NAT instances in each AZ behind an Auto Scaling group.
Why wrong: NAT instances require management overhead and are less cost-effective.
- C
Place web servers in public subnets and application/database servers in private subnets in one AZ. Use a single NAT Gateway in the public subnet for outbound traffic.
Why wrong: Single AZ is not highly available; single NAT Gateway is a SPOF.
- D
Place all tiers in public subnets and use security groups to restrict inbound traffic to the web tier only.
Why wrong: Public subnets expose instances to the internet; not secure.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 network for a three-tier web application in AWS. The web tier must be accessible from the internet, but the application and database tiers must be private. The company wants to use a single AWS Region and ensure high availability across multiple Availability Zones. What is the MOST cost-effective network design that meets these requirements?
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
Place web servers in public subnets across three AZs. Place application and database servers in private subnets across three AZs. Use a NAT Gateway in each AZ for outbound traffic.
Option A is correct because it places web servers in public subnets across three Availability Zones (AZs) for internet-facing access and high availability, while application and database servers reside in private subnets across three AZs for isolation. A NAT Gateway in each AZ provides cost-effective outbound internet connectivity for private instances without exposing them to inbound traffic, and using one NAT Gateway per AZ avoids cross-AZ data transfer charges, which would increase costs if a single NAT Gateway were shared across AZs.
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.
- ✓
Place web servers in public subnets across three AZs. Place application and database servers in private subnets across three AZs. Use a NAT Gateway in each AZ for outbound traffic.
Why this is correct
Highly available and cost-effective managed service.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Place web servers in public subnets across three AZs. Place application and database servers in private subnets across three AZs. Use NAT instances in each AZ behind an Auto Scaling group.
Why it's wrong here
NAT instances require management overhead and are less cost-effective.
- ✗
Place web servers in public subnets and application/database servers in private subnets in one AZ. Use a single NAT Gateway in the public subnet for outbound traffic.
- ✗
Place all tiers in public subnets and use security groups to restrict inbound traffic to the web tier only.
Why it's wrong here
Public subnets expose instances to the internet; not secure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the misconception that a single NAT Gateway is more cost-effective than multiple, but the trap is that cross-AZ data transfer costs from using a single NAT Gateway in a multi-AZ setup can exceed the cost of deploying one NAT Gateway per AZ, making the per-AZ design more cost-effective overall.
Detailed technical explanation
How to think about this question
NAT Gateways are managed by AWS and automatically scale up to 45 Gbps, but they incur hourly charges and data processing fees; using one per AZ avoids cross-AZ data transfer costs (typically $0.01–$0.02 per GB) that would accrue if private instances in one AZ routed outbound traffic through a NAT Gateway in another AZ. In a three-tier architecture, the database tier often requires outbound access for patches or updates, and NAT Gateways provide this without exposing the database to inbound internet traffic, aligning with the principle of least privilege. For high availability, distributing resources across three AZs ensures that even if one AZ fails, the remaining two can sustain the workload, though two AZs are often sufficient for most SLAs.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
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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: Place web servers in public subnets across three AZs. Place application and database servers in private subnets across three AZs. Use a NAT Gateway in each AZ for outbound traffic. — Option A is correct because it places web servers in public subnets across three Availability Zones (AZs) for internet-facing access and high availability, while application and database servers reside in private subnets across three AZs for isolation. A NAT Gateway in each AZ provides cost-effective outbound internet connectivity for private instances without exposing them to inbound traffic, and using one NAT Gateway per AZ avoids cross-AZ data transfer charges, which would increase costs if a single NAT Gateway were shared across AZs.
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.
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 →
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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