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 company uses an AWS Lambda function to process files uploaded to an S3 bucket. The Lambda function needs to read the files and write results to a DynamoDB table. The Lambda function is configured with an IAM role that has policies allowing s3:GetObject on the bucket and dynamodb:PutItem on the table. Despite correct permissions, the function fails with an AccessDenied error when trying to put items. 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 DynamoDB table has a resource-based policy that explicitly denies access to the Lambda function's IAM role.
The correct answer is B because DynamoDB tables can have resource-based policies that explicitly deny access even if the IAM role has the necessary permissions. Since explicit denies in resource-based policies override any allow in identity-based policies, the Lambda function's IAM role with dynamodb:PutItem permission is still blocked, causing the AccessDenied error.
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 Lambda function is in a VPC without a VPC endpoint for DynamoDB.
Why it's wrong here
Lambda can access DynamoDB via internet or VPC endpoint, but this would cause timeout, not AccessDenied.
✓
The DynamoDB table has a resource-based policy that explicitly denies access to the Lambda function's IAM role.
Why this is correct
Resource-based policies can override IAM permissions.
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.
✗
The S3 bucket is in a different region, causing cross-region access issues.
Why it's wrong here
S3 event triggers work cross-region, but DynamoDB access is not affected.
✗
The DynamoDB table is encrypted with a customer managed KMS key, and the Lambda role does not have kms:Decrypt permission.
Why it's wrong here
Would cause AccessDenied, but likely less common than resource-based policy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume IAM role permissions alone guarantee access, forgetting that resource-based policies on DynamoDB tables can explicitly deny access, which overrides any allow in identity-based policies.
Detailed technical explanation
How to think about this question
DynamoDB resource-based policies (also called table policies) are evaluated after IAM identity-based policies, and an explicit deny in a resource-based policy always takes precedence over any allow, following the AWS IAM policy evaluation logic. This is a common security pattern to restrict access to specific principals or conditions, such as denying access from certain IP ranges or roles, and can cause unexpected failures if the policy is misconfigured. In practice, you can check the DynamoDB table's 'Permissions' tab in the console to see if a resource-based policy exists that might be blocking the Lambda role.
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 DynamoDB table has a resource-based policy that explicitly denies access to the Lambda function's IAM role. — The correct answer is B because DynamoDB tables can have resource-based policies that explicitly deny access even if the IAM role has the necessary permissions. Since explicit denies in resource-based policies override any allow in identity-based policies, the Lambda function's IAM role with dynamodb:PutItem permission is still blocked, causing the AccessDenied error.
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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