The answer is that the requests are being denied because the EC2 instance is not routing traffic through the VPC endpoint, instead using the public S3 endpoint. The `aws:SourceVpce` condition key only appears in a request when the traffic actually traverses the VPC endpoint; if an instance uses the public internet or a NAT gateway to reach S3, the condition key is absent from the request, causing the bucket policy’s allow statement to fail. This scenario tests your understanding of how VPC endpoint conditions interact with routing—a common trap on the AWS Certified Security Specialty SCS-C02 exam is assuming that simply having the correct VPC endpoint ID in the policy guarantees access, when in fact the request must physically pass through that endpoint for the condition to evaluate. A key memory tip: “If it doesn’t go through the endpoint, the condition key won’t be sent.”
SCS-C02 Management and Security Governance Practice Question
This SCS-C02 practice question tests your understanding of management and security governance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has an S3 bucket that stores sensitive data. The bucket policy allows access only from a specific VPC endpoint. The security engineer tests the configuration and finds that requests from the VPC endpoint are being denied. The bucket policy contains the following condition: "Condition": { "StringEquals": { "aws:SourceVpce": "vpce-12345678" } }. The VPC endpoint ID is correct. The engineer also confirms that the VPC endpoint policy allows the necessary S3 actions. What is the most likely reason for the denial?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The request is not being routed through the VPC endpoint; the EC2 instance is using a public S3 endpoint.
Option B is correct because the key should be aws:SourceVpce, not aws:SourceVpce. Wait, the condition uses aws:SourceVpce, which is correct. However, the condition might need to be combined with an Allow. The most common issue is that the bucket policy also has a Deny for public access, but the VPC endpoint request might not include the condition key if the request is not made through the endpoint. Option A: The VPC endpoint might be in a different region, but that would not cause denial; S3 supports cross-region access. Option C: The condition key is correct. Option D: The IAM role is needed but not necessarily. Actually, the most likely issue is that the bucket policy is missing an explicit Allow for the VPC endpoint; the condition alone does not grant access. The policy must have an Allow statement with the condition. If the policy only has a Deny or the Allow does not include the condition, it might fail. But the question says the policy allows access only from that VPC endpoint, implying there is an Allow with that condition. Another common issue: the VPC endpoint DNS name resolves to public IP, but the condition aws:SourceVpce is only present if the request goes through the endpoint. If the request originates from an EC2 instance in the VPC but does not use the endpoint, the condition is not met. Option A is plausible: the EC2 instance might be accessing S3 via the public internet instead of through the endpoint. That would cause the condition to fail. So Option A is correct.
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.
✓
The request is not being routed through the VPC endpoint; the EC2 instance is using a public S3 endpoint.
Why this is correct
If not using endpoint, the condition key is not present.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The EC2 instance does not have an IAM role that allows s3:GetObject.
Why it's wrong here
The bucket policy should grant access regardless of IAM role.
✗
The VPC endpoint is in a different region than the S3 bucket.
Why it's wrong here
S3 supports cross-region VPC endpoints.
✗
The condition key is misspelled; it should be aws:SourceVpce (no 'e' at the end).
Why it's wrong here
Condition key is correct.
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 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 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 SCS-C02 NAT questions on configuration and troubleshooting.
Management and Security Governance — This question tests Management and Security Governance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The request is not being routed through the VPC endpoint; the EC2 instance is using a public S3 endpoint. — Option B is correct because the key should be aws:SourceVpce, not aws:SourceVpce. Wait, the condition uses aws:SourceVpce, which is correct. However, the condition might need to be combined with an Allow. The most common issue is that the bucket policy also has a Deny for public access, but the VPC endpoint request might not include the condition key if the request is not made through the endpoint. Option A: The VPC endpoint might be in a different region, but that would not cause denial; S3 supports cross-region access. Option C: The condition key is correct. Option D: The IAM role is needed but not necessarily. Actually, the most likely issue is that the bucket policy is missing an explicit Allow for the VPC endpoint; the condition alone does not grant access. The policy must have an Allow statement with the condition. If the policy only has a Deny or the Allow does not include the condition, it might fail. But the question says the policy allows access only from that VPC endpoint, implying there is an Allow with that condition. Another common issue: the VPC endpoint DNS name resolves to public IP, but the condition aws:SourceVpce is only present if the request goes through the endpoint. If the request originates from an EC2 instance in the VPC but does not use the endpoint, the condition is not met. Option A is plausible: the EC2 instance might be accessing S3 via the public internet instead of through the endpoint. That would cause the condition to fail. So Option A is correct.
What should I do if I get this SCS-C02 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 SCS-C02 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". 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?
Static NAT maps one inside address to one outside address.
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