- A
NAT gateway in the public subnet
Why wrong: NAT gateway is not needed because web servers are in a public subnet and can use the Internet gateway for outbound internet access.
- B
Network ACL for subnets
Network ACLs are essential for subnet-level security, controlling traffic between public and private subnets.
- C
Internet gateway
Internet gateway is essential for web servers in the public subnet to access the internet.
- D
VPC endpoint for S3
Why wrong: VPC endpoint for S3 is not essential for this architecture; internet updates can be obtained via the Internet gateway.
- E
Security groups for web and database servers
Security groups are essential to restrict database servers to only accept traffic from web servers.
Question 929 of 1,705
Essential VPC Components for Public/Private Subnet Architecture
This ANS-C01 practice question tests your understanding of network implementation. 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. A key principle to apply: internet Gateway. 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 deploying a new VPC with public and private subnets. The VPC will host web servers in the public subnet and database servers in the private subnet. The web servers need to access the internet for updates, and the database servers need to receive traffic only from the web servers. Which THREE components are essential for this architecture?
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
✓
Network ACL for subnets
An internet gateway (IGW) is essential to allow web servers in the public subnet to directly access the internet. Security groups are essential to control traffic between web and database servers, ensuring only web servers can access the database. Network ACLs are essential for subnet-level traffic control, such as allowing inbound traffic from the public subnet to the private subnet while denying other inbound traffic. A NAT gateway is not essential because the database servers do not require outbound internet access (only web servers need internet for updates). A VPC endpoint for S3 is not essential as there is no requirement to access S3.
Key principle: Internet Gateway
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NAT gateway in the public subnet
- ✓
Network ACL for subnets
Why this is correct
Network ACLs are essential for subnet-level security, controlling traffic between public and private subnets.
Related concept
Internet Gateway
- ✓
Internet gateway
- ✗
VPC endpoint for S3
Why it's wrong here
VPC endpoint for S3 is not essential for this architecture; internet updates can be obtained via the Internet gateway.
- ✓
Security groups for web and database servers
Why this is correct
Security groups are essential to restrict database servers to only accept traffic from web servers.
Related concept
Internet Gateway
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often mistakenly think a NAT gateway is required for the private subnet, but the database servers do not need internet access. Additionally, they may overlook Network ACLs as essential because security groups alone can allow traffic between web and database instances, but Network ACLs provide subnet-level control required by the architecture.
Detailed technical explanation
How to think about this question
The NAT gateway operates at the network layer (Layer 3) and performs port address translation (PAT), translating private source IPs to the gateway's Elastic IP for outbound traffic. It maintains stateful connection tracking so that response traffic is correctly forwarded back to the originating instance, but it does not allow unsolicited inbound traffic, which is a key security property. In a real-world scenario, if the web servers need to download patches from a public repository, the NAT gateway ensures that the update traffic flows out through the internet gateway while the database servers remain isolated in the private subnet with no direct internet path.
KKey Concepts to Remember
- Internet Gateway
- Network ACL
- Security Group
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Internet Gateway
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.
Visual reference
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Internet Gateway.
What is the correct answer to this question?
The correct answer is: Network ACL for subnets — An internet gateway (IGW) is essential to allow web servers in the public subnet to directly access the internet. Security groups are essential to control traffic between web and database servers, ensuring only web servers can access the database. Network ACLs are essential for subnet-level traffic control, such as allowing inbound traffic from the public subnet to the private subnet while denying other inbound traffic. A NAT gateway is not essential because the database servers do not require outbound internet access (only web servers need internet for updates). A VPC endpoint for S3 is not essential as there is no requirement to access S3.
What should I do if I get this ANS-C01 question wrong?
Review internet Gateway, then practise related ANS-C01 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Internet Gateway
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Last reviewed: Jul 4, 2026
This ANS-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 ANS-C01 exam.
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