- A
The Gateway VPC Endpoint is in a different region than the S3 bucket
Why wrong: Incorrect; Gateway Endpoints are regional and S3 bucket is in the same region.
- B
The security group for the EC2 instances does not allow outbound traffic to the S3 prefix list
Why wrong: Incorrect; the security group allows outbound HTTPS to 0.0.0.0/0, which includes S3.
- C
The S3 bucket policy does not include a condition for the VPC endpoint
Why wrong: Incorrect; the bucket policy allows access from the VPC endpoint.
- D
The route to the Gateway VPC Endpoint was added only to public subnets, not to private subnets
Correct; the route must be in the private subnet route table for EC2 instances to use the endpoint.
Question 967 of 1,705
ANS-C01 Gateway VPC Endpoint Practice Question
This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: gateway VPC Endpoint. 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 has a production VPC with CIDR 10.0.0.0/16. They have an internet-facing Application Load Balancer (ALB) in public subnets across two Availability Zones. The ALB distributes traffic to a fleet of EC2 instances in private subnets. The EC2 instances need to access an Amazon S3 bucket to retrieve configuration files. The company wants to minimize data transfer costs and ensure that traffic to S3 does not traverse the internet. A network engineer created a Gateway VPC Endpoint for S3 in the VPC and added a route in the public subnet route tables pointing to the endpoint. However, the EC2 instances still cannot access the S3 bucket. The security groups for the EC2 instances allow outbound HTTPS to 0.0.0.0/0. The NACLs are default (allow all). The S3 bucket policy allows access from the VPC endpoint. What is the MOST likely reason the EC2 instances cannot access S3?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
✓
The route to the Gateway VPC Endpoint was added only to public subnets, not to private subnets
The correct answer is D. The Gateway VPC Endpoint for S3 must have a route in the route tables of the subnets where the EC2 instances reside. The engineer added the route only to public subnet route tables, not the private subnets. Therefore, traffic from the EC2 instances to S3 still uses the default route (0.0.0.0/0) via NAT Gateway or Internet Gateway, not the VPC endpoint. Option A is incorrect because the endpoint is in the same region. Option B is incorrect because the security group allows outbound HTTPS to all destinations. Option C is incorrect because the S3 bucket policy includes the necessary condition.
Key principle: Gateway VPC Endpoint
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The Gateway VPC Endpoint is in a different region than the S3 bucket
Why it's wrong here
Incorrect; Gateway Endpoints are regional and S3 bucket is in the same region.
- ✗
The security group for the EC2 instances does not allow outbound traffic to the S3 prefix list
Why it's wrong here
Incorrect; the security group allows outbound HTTPS to 0.0.0.0/0, which includes S3.
- ✗
The S3 bucket policy does not include a condition for the VPC endpoint
Why it's wrong here
Incorrect; the bucket policy allows access from the VPC endpoint.
- ✓
The route to the Gateway VPC Endpoint was added only to public subnets, not to private subnets
Why this is correct
Correct; the route must be in the private subnet route table for EC2 instances to use the endpoint.
Clue confirmation
The clue words "most likely", "minimum / minimize" in the question point toward this answer.
Related concept
Gateway VPC Endpoint
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common trap is to think that adding a route to any subnet is sufficient. However, the route must be in the route table of the subnet where the instance resides. Public subnets have routes to the internet gateway, but private subnets need explicit routes to the gateway endpoint.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Gateway VPC Endpoint
- Route Table Association
- S3 Bucket Policy
- Private Subnet Routing
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
Gateway VPC Endpoint
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Gateway VPC Endpoint.
What is the correct answer to this question?
The correct answer is: The route to the Gateway VPC Endpoint was added only to public subnets, not to private subnets — The correct answer is D. The Gateway VPC Endpoint for S3 must have a route in the route tables of the subnets where the EC2 instances reside. The engineer added the route only to public subnet route tables, not the private subnets. Therefore, traffic from the EC2 instances to S3 still uses the default route (0.0.0.0/0) via NAT Gateway or Internet Gateway, not the VPC endpoint. Option A is incorrect because the endpoint is in the same region. Option B is incorrect because the security group allows outbound HTTPS to all destinations. Option C is incorrect because the S3 bucket policy includes the necessary condition.
What should I do if I get this ANS-C01 question wrong?
Review gateway VPC Endpoint, then practise related ANS-C01 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "minimum / minimize". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Gateway VPC Endpoint
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Last reviewed: Jun 20, 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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