- A
Place all application resources in a VPC with no internet gateway and use VPC endpoints for AWS services
Why wrong: This limits exposure but does not fulfill PCI DSS encryption and access control requirements.
- B
Use a cloud-based web application firewall (WAF) and enable logging for all API calls
Why wrong: A WAF protects against web attacks but does not cover data-at-rest encryption or key management.
- C
Deploy the application on a single tenant dedicated instance and rely on the cloud provider's compliance certifications
Why wrong: This does not address specific PCI DSS controls like encryption and access management.
- D
Implement a cloud access security broker (CASB) and use customer-managed encryption keys (CMKs) for data at rest
CASB provides visibility and policy enforcement; CMKs meet PCI DSS encryption requirements.
Quick Answer
The correct choice is to implement a cloud access security broker (CASB) and use customer-managed encryption keys (CMKs) for data at rest. This architecture directly supports PCI DSS compliance by ensuring the financial institution retains sole control over encryption keys, meeting the requirement for strong cryptography on stored cardholder data, while the CASB provides the necessary visibility and policy enforcement over cloud traffic to detect misconfigurations or unauthorized access. On the CompTIA SecurityX CAS-004 exam, this question tests your ability to balance security controls with operational efficiency in a cloud-native environment—a common trap is selecting a web application firewall (WAF) or VPC endpoints, which address network threats but do not satisfy the data-at-rest encryption mandate. Remember the mnemonic “C-KEY” for Cloud-native, Keys, Encryption, and You control compliance.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. 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 architect at a financial institution is designing a cloud-native application using AWS. The application processes sensitive customer data and must comply with PCI DSS. Which of the following security architecture decisions best supports both compliance and operational efficiency?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Implement a cloud access security broker (CASB) and use customer-managed encryption keys (CMKs) for data at rest
Using a CASB provides visibility and control over cloud traffic, and encryption with customer-managed keys satisfies PCI DSS requirements. Option A is wrong because ignoring cloud risks is not acceptable. Option B is wrong because a cloud-based WAF is not specifically for data protection compliance. Option D is wrong because VPC endpoints reduce exposure but do not address data protection requirements directly.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Place all application resources in a VPC with no internet gateway and use VPC endpoints for AWS services
Why it's wrong here
This limits exposure but does not fulfill PCI DSS encryption and access control requirements.
- ✗
Use a cloud-based web application firewall (WAF) and enable logging for all API calls
Why it's wrong here
A WAF protects against web attacks but does not cover data-at-rest encryption or key management.
- ✗
Deploy the application on a single tenant dedicated instance and rely on the cloud provider's compliance certifications
Why it's wrong here
This does not address specific PCI DSS controls like encryption and access management.
- ✓
Implement a cloud access security broker (CASB) and use customer-managed encryption keys (CMKs) for data at rest
Why this is correct
CASB provides visibility and policy enforcement; CMKs meet PCI DSS encryption requirements.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this CAS-004 question test?
Security Architecture — This question tests Security Architecture — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Implement a cloud access security broker (CASB) and use customer-managed encryption keys (CMKs) for data at rest — Using a CASB provides visibility and control over cloud traffic, and encryption with customer-managed keys satisfies PCI DSS requirements. Option A is wrong because ignoring cloud risks is not acceptable. Option B is wrong because a cloud-based WAF is not specifically for data protection compliance. Option D is wrong because VPC endpoints reduce exposure but do not address data protection requirements directly.
What should I do if I get this CAS-004 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA 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 CAS-004 exam.
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