This DVA-C02 practice question tests your understanding of security. 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 developer is troubleshooting an issue where an EC2 instance cannot access an S3 bucket even though the instance has an IAM role with full S3 access. The instance can access the internet. What is the most likely cause?
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 instance is in a private subnet without a NAT gateway or VPC endpoint for S3.
The most likely cause is that the EC2 instance resides in a private subnet, which has no direct route to the internet or to S3. Without a NATgateway or a VPC endpoint for S3, the instance cannot reach the S3 API endpoints, even though it has an IAM role granting full S3 access. The instance's ability to access the internet is irrelevant if it's in a private subnet, as internet traffic must go through a NAT device or a VPC endpoint.
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.
✓
The instance is in a private subnet without a NAT gateway or VPC endpoint for S3.
Why this is correct
Private subnets need a NATgateway or VPC endpoint to reach S3.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
S3 Transfer Acceleration is not enabled on the bucket.
Why it's wrong here
Transfer Acceleration is optional and not required for access.
✗
The security group attached to the instance blocks outbound traffic to S3.
Why it's wrong here
Security groups don't apply to S3 endpoints.
✗
The IAM role is not correctly associated with the instance.
Why it's wrong here
The role is associated, as stated.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume that an IAM role with full S3 access is sufficient for an EC2 instance to access S3, overlooking the critical requirement of network connectivity, especially when the instance is in a private subnet without a NATgateway or VPC endpoint.
Detailed technical explanation
How to think about this question
When an EC2 instance is launched in a private subnet, it has no public IP address and no route to an internet gateway. To access AWS services like S3, which are accessed via public endpoints, the instance must either use a NAT gateway (which provides outbound internet access) or a VPC endpoint for S3 (which provides private connectivity to S3 without traversing the internet). The IAM role provides the necessary permissions, but without a network path, the requests cannot reach S3. This is a common misconfiguration in VPC design, especially when developers assume that an IAM role alone is sufficient for service access.
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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The instance is in a private subnet without a NAT gateway or VPC endpoint for S3. — The most likely cause is that the EC2 instance resides in a private subnet, which has no direct route to the internet or to S3. Without a NAT gateway or a VPC endpoint for S3, the instance cannot reach the S3 API endpoints, even though it has an IAM role granting full S3 access. The instance's ability to access the internet is irrelevant if it's in a private subnet, as internet traffic must go through a NAT device or a VPC endpoint.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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