The answer is to use security groups to control traffic between tiers and implement AWS WAF to protect against web exploits. Security groups act as a virtual firewall at the instance level, allowing you to enforce least-privilege access by restricting inbound and outbound traffic strictly between the web, application, and database layers, while AWS WAF provides a managed rule set to filter and block common attack patterns like SQL injection and cross-site scripting at the application edge. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this question tests your understanding of network segmentation and application-layer defense within a secure three-tier web application AWS architecture, with a common trap being the mistaken belief that placing all tiers in public subnets or granting the database tier direct internet access is acceptable. Remember the memory tip: “WAF at the front, SGs between the tiers” to keep your layers isolated and your web app protected.
PAS-C01 Migration Practice Question
This PAS-C01 practice question tests your understanding of migration. 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 migrating a web application to AWS and wants to improve security. The application uses a classic three-tier architecture. Which TWO security measures should the company implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS WAF to protect the web tier
Using security groups as a virtual firewall and AWS WAF to protect against common web exploits are both security best practices. Option A (Direct internet access for database tier) is insecure. Option B (S3 Transfer Acceleration) is for speed, not security. Option E (Public subnets for all tiers) is insecure.
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.
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 PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Migration — This question tests Migration — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Use AWS WAF to protect the web tier — Using security groups as a virtual firewall and AWS WAF to protect against common web exploits are both security best practices. Option A (Direct internet access for database tier) is insecure. Option B (S3 Transfer Acceleration) is for speed, not security. Option E (Public subnets for all tiers) is insecure.
What should I do if I get this PAS-C01 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 PAS-C01 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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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.
Question Discussion
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