The answer is a NAT Gateway in a public subnet combined with an S3 Gateway Endpoint in the VPC. The NAT Gateway enables outbound internet traffic from private instances without allowing any unsolicited inbound connections, while the S3 Gateway Endpoint provides private, cost-free access to S3 within the same region, bypassing the internet entirely. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how to architect secure outbound connectivity and private AWS service access without public IPs—a common trap is confusing the S3 Gateway Endpoint with an Interface Endpoint, but S3 only supports the Gateway type. Remember the mnemonic: "NAT for out, Gateway for S3 without a doubt."
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 security engineer is designing a VPC with public and private subnets. The application must be able to send outbound traffic to the internet, but inbound traffic from the internet must be blocked except for a single HTTP load balancer. The application also needs to access an S3 bucket in the same AWS region. Which combination of VPC components meets these requirements? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NAT Gateway in a public subnet
Option A (NATGateway in public subnet) allows outbound internet. Option C (S3 Gateway Endpoint) provides private access to S3. Option B is wrong because Internet Gateway alone would allow inbound. Option D is wrong because VPC Peering is not needed. Option E is wrong because VPC Endpoint (Interface) for S3 is not supported; S3 uses Gateway Endpoint.
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.
✗
S3 Interface Endpoint in the VPC
Why it's wrong here
S3 does not support Interface Endpoints; only Gateway Endpoints are used.
✗
VPC Peering to a shared services VPC
Why it's wrong here
Not required for S3 access.
✓
NAT Gateway in a public subnet
Why this is correct
Allows outbound internet to EC2 instances in private subnets.
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.
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: NAT Gateway in a public subnet — Option A (NAT Gateway in public subnet) allows outbound internet. Option C (S3 Gateway Endpoint) provides private access to S3. Option B is wrong because Internet Gateway alone would allow inbound. Option D is wrong because VPC Peering is not needed. Option E is wrong because VPC Endpoint (Interface) for S3 is not supported; S3 uses Gateway Endpoint.
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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Question Discussion
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