The answer is to create a VPC Gateway Endpoint for S3 and add a route in the private subnet’s route table pointing to the endpoint. This solution is correct because a VPC Gateway Endpoint enables private S3 access by allowing EC2 instances in private subnets to reach S3 over the AWS backbone network, completely bypassing the internet. Since the instances already have an instance profile granting write access, the missing piece is the network path—the gateway endpoint provides that path without requiring a NAT gateway or internet gateway. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of when to use a Gateway Endpoint versus an Interface Endpoint; the key distinction is that Gateway Endpoints use route table entries and are free, while Interface Endpoints use ENIs and incur hourly costs. A common trap is choosing a NAT gateway or VPC peering, which would either introduce internet transit or be unnecessary. Memory tip: Gateway Endpoints are for S3 and DynamoDB only—think "Gateway goes in the route table, Interface goes in the subnet."
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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 deploying a multi-tier web application in a VPC. The architecture includes an internet-facing Application Load Balancer (ALB) in public subnets, a fleet of EC2 instances in private subnets, and an Amazon RDS database in a separate private subnet. The security team requires that the web application logs be stored in an Amazon S3 bucket for compliance. The EC2 instances have an instance profile that grants write access to the S3 bucket. The EC2 instances are in a private subnet that does not have a route to the internet. The company wants to ensure that the EC2 instances can upload logs to the S3 bucket without traversing the internet. Which solution should they implement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a VPC Gateway Endpoint for S3 and add a route in the private subnet's route table pointing to the endpoint
A VPC Gateway Endpoint for S3 allows EC2 instances in private subnets to access S3 over the AWS network without traversing the internet. Since the instances have an instance profile granting write access, adding a route in the private subnet's route table pointing to the gateway endpoint enables direct, private connectivity to S3. This meets the security requirement of keeping traffic within the AWS backbone.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Create a VPC Gateway Endpoint for S3 and add a route in the private subnet's route table pointing to the endpoint
Why this is correct
Gateway Endpoint provides private access to S3 without internet.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a VPC Interface Endpoint for S3
Why it's wrong here
Interface Endpoint is for services like API Gateway, not S3.
✗
Deploy a forward proxy server in a public subnet and configure the EC2 instances to use it
Why it's wrong here
Proxy server would require internet access.
✗
Attach a NAT Gateway to the private subnet and configure a route to the NAT Gateway
Why it's wrong here
NATGateway provides internet access, which is not desired.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse VPC Gateway Endpoints with Interface Endpoints, assuming Interface Endpoints are always required for private access, but Gateway Endpoints are the correct, cost-effective choice for S3 and DynamoDB from private subnets without internet.
Detailed technical explanation
How to think about this question
VPC Gateway Endpoints use prefix lists and route table entries to direct S3 traffic over the AWS network, leveraging the S3 service's public IP addresses but routing them through the AWS backbone rather than the internet. This is achieved by adding a route in the subnet's route table with the destination as the S3 prefix list (e.g., com.amazonaws.region.s3) and the target as the gateway endpoint ID. The EC2 instances' instance profile provides IAM credentials that are automatically rotated by the AWS credentials service, ensuring secure, private access without needing internet connectivity.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a VPC Gateway Endpoint for S3 and add a route in the private subnet's route table pointing to the endpoint — A VPC Gateway Endpoint for S3 allows EC2 instances in private subnets to access S3 over the AWS network without traversing the internet. Since the instances have an instance profile granting write access, adding a route in the private subnet's route table pointing to the gateway endpoint enables direct, private connectivity to S3. This meets the security requirement of keeping traffic within the AWS backbone.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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