Quick Answer
The correct choice is to place the database tier in private subnets. This configuration ensures the database tier remains private from the internet because private subnets have no direct route to an internet gateway, blocking all inbound traffic from the public internet while still allowing outbound traffic through a NAT gateway if needed. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of VPC design for multi-tier applications, specifically how to isolate sensitive components like databases from public exposure. A common trap is confusing private subnets with public subnets or assuming a NAT gateway provides inbound internet access—it does not; NAT gateways only enable outbound internet for resources in private subnets. Remember the memory tip: “Private subnets keep the database hidden; public subnets leave it open.”
This PAS-C01 practice question tests your understanding of migration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 migrating a multi-tier application to AWS. The application includes a web tier, application tier, and database tier. To ensure security, the database tier must not be accessible from the internet. Which VPC configuration should be used?
Place the database tier in subnets with a NAT Gateway
Why wrong: NAT Gateway provides outbound internet, not inbound isolation.
Place the database tier in subnets with an Internet Gateway
Why wrong: Internet Gateway provides inbound internet access.
Place all tiers in public subnets
Why wrong: Would expose database to internet.
Place the database tier in private subnets
Private subnets have no direct internet access.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Place the database tier in private subnets
Placing the database tier in private subnets ensures it is not directly accessible from the internet. Option A (Public subnets) would allow internet access. Option B (NAT Gateway) is for outbound internet. Option D (Internet Gateway) is for inbound/outbound internet access.
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
For each option: why learners choose it and why it is or isn't the right answer here.
Place the database tier in subnets with a NAT Gateway
Place the database tier in subnets with an Internet Gateway
Why it's wrong here
Internet Gateway provides inbound internet access.
Place all tiers in public subnets
Why it's wrong here
Would expose database to internet.
Place the database tier in private subnets
Why this is correct
Private subnets have no direct internet access.
Related concept
CIDR notation defines the prefix length.
Common exam traps
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
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.
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
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
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Migration — This question tests Migration — CIDR notation defines the prefix length..
The correct answer is: Place the database tier in private subnets — Placing the database tier in private subnets ensures it is not directly accessible from the internet. Option A (Public subnets) would allow internet access. Option B (NAT Gateway) is for outbound internet. Option D (Internet Gateway) is for inbound/outbound internet access.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
This PAS-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 PAS-C01 exam.
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