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 a single VPC. The web tier must be accessible from the internet, but the application and database tiers must not have direct internet access. The application servers need to make outbound calls to a third-party API. Which architecture meets these requirements?
Web servers in public subnets, application and database servers in private subnets with an internet gateway for outbound traffic.
Why wrong: Private subnets need a NAT device for outbound internet access, not an internet gateway.
B
All servers in public subnets with security groups restricting access.
Why wrong: Public subnets expose application and database servers unnecessarily.
C
Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets.
This follows best practices for a three-tier architecture.
D
All servers in private subnets and a VPN connection to the internet.
Why wrong: A VPN to the internet is not a standard solution for outbound traffic.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets.
Option C is correct because it places web servers in public subnets with an Application Load Balancer for inbound internet traffic, while application and database servers reside in private subnets without direct internet access. A NATgateway in a public subnet enables the application servers to initiate outbound connections to a third-party API, with return traffic automatically routed back, meeting the requirement for outbound-only internet access.
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.
✗
Web servers in public subnets, application and database servers in private subnets with an internet gateway for outbound traffic.
Why it's wrong here
Private subnets need a NAT device for outbound internet access, not an internet gateway.
✗
All servers in public subnets with security groups restricting access.
Why it's wrong here
Public subnets expose application and database servers unnecessarily.
✓
Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets.
Why this is correct
This follows best practices for a three-tier architecture.
Related concept
Read the scenario before looking for a memorised answer.
✗
All servers in private subnets and a VPN connection to the internet.
Why it's wrong here
A VPN to the internet is not a standard solution for outbound traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse an internet gateway with a NAT gateway, assuming an internet gateway can provide outbound-only access from private subnets, but an internet gateway requires public IPs and allows bidirectional traffic, while a NAT gateway specifically enables outbound-only traffic from private subnets.
Detailed technical explanation
How to think about this question
A NATgateway operates at Layer 3/4, translating private IPs to the public IP of the NAT gateway for outbound traffic and using connection tracking to return responses to the correct private instance. The Application Load Balancer (ALB) terminates HTTP/HTTPS traffic at Layer 7, distributing requests to web servers in public subnets while keeping the application tier isolated. In real-world scenarios, if the third-party API requires IP whitelisting, the NAT gateway's Elastic IP provides a stable source address for outbound calls.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: Web servers in public subnets with an Application Load Balancer, application servers in private subnets with a NAT gateway, and database servers in private subnets. — Option C is correct because it places web servers in public subnets with an Application Load Balancer for inbound internet traffic, while application and database servers reside in private subnets without direct internet access. A NAT gateway in a public subnet enables the application servers to initiate outbound connections to a third-party API, with return traffic automatically routed back, meeting the requirement for outbound-only internet access.
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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Question Discussion
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