- A
Web servers in private subnets, database servers in public subnets, both behind an Application Load Balancer
Why wrong: Database servers are publicly accessible, which violates the requirement.
- B
Web servers in public subnets, database servers in private subnets with a route to a NAT Gateway in a public subnet
Why wrong: Database servers would have outbound internet access, violating the requirement.
- C
Web servers in private subnets with a route to a NAT Gateway, database servers in private subnets with no route to the NAT Gateway, both behind an Application Load Balancer in public subnets
Web servers can reach the internet via NAT, database servers have no internet access, and the ALB handles HTTPS traffic.
- D
Web servers in public subnets with Elastic IPs, database servers in private subnets with a route to an internet gateway
Why wrong: Web servers are publicly accessible, but database servers would also have internet access via the route to the internet gateway.
Quick Answer
The correct choice is a three-tier VPC design with NAT Gateway, where web servers reside in private subnets with a route to a NAT Gateway for outbound internet access, database servers are in separate private subnets with no such route, and an Application Load Balancer in public subnets handles inbound HTTPS traffic. This architecture satisfies the requirement because the NAT Gateway enables the web servers to initiate outbound connections for software updates while keeping them inaccessible from the internet, and the database servers are completely isolated from any internet path, preventing both inbound and outbound direct access. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of subnet segmentation, NAT Gateway placement, and the principle of least privilege for data tiers. A common trap is assuming web servers must be in public subnets to receive traffic, but the ALB in public subnets handles that, while the web servers stay private for security. Remember the memory tip: “ALB in public, web in private with NAT, DB in private with no route—keep the data plane locked down.”
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. 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 VPC for a three-tier web application that must be accessible from the internet only via HTTPS. The web servers must be able to initiate outbound connections to the internet for software updates, but the database servers must have no direct internet access. Which architecture 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
Web servers in private subnets with a route to a NAT Gateway, database servers in private subnets with no route to the NAT Gateway, both behind an Application Load Balancer in public subnets
Option D is correct because it uses a public subnet for the NAT Gateway and the ALB, private subnets for web servers (with a route to NAT for outbound) and database servers (no route to NAT). Option A is wrong because it gives database servers a route to NAT. Option B is wrong because it places web servers in public subnets with direct internet access, which is less secure. Option C is wrong because it places database servers in public subnets.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 private subnets, database servers in public subnets, both behind an Application Load Balancer
Why it's wrong here
Database servers are publicly accessible, which violates the requirement.
- ✗
Web servers in public subnets, database servers in private subnets with a route to a NAT Gateway in a public subnet
Why it's wrong here
Database servers would have outbound internet access, violating the requirement.
- ✓
Web servers in private subnets with a route to a NAT Gateway, database servers in private subnets with no route to the NAT Gateway, both behind an Application Load Balancer in public subnets
- ✗
Web servers in public subnets with Elastic IPs, database servers in private subnets with a route to an internet gateway
Why it's wrong here
Web servers are publicly accessible, but database servers would also have internet access via the route to the internet gateway.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Web servers in private subnets with a route to a NAT Gateway, database servers in private subnets with no route to the NAT Gateway, both behind an Application Load Balancer in public subnets — Option D is correct because it uses a public subnet for the NAT Gateway and the ALB, private subnets for web servers (with a route to NAT for outbound) and database servers (no route to NAT). Option A is wrong because it gives database servers a route to NAT. Option B is wrong because it places web servers in public subnets with direct internet access, which is less secure. Option C is wrong because it places database servers in public subnets.
What should I do if I get this SCS-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
This SCS-C02 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 SCS-C02 exam.
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