The answer is the key policy condition `kms:ViaService` restricts KMS actions to only those made through S3, but AWS Glue calls KMS directly, not via S3. This condition is designed to allow KMS operations only when the request originates from a specified AWS service, such as S3, by checking the `kms:ViaService` key. However, when an AWS Glue job reads encrypted data from S3, it first calls KMS directly to decrypt the S3 object’s data key, rather than having S3 proxy the request. Because the Glue job’s KMS request does not come from the S3 service, the condition fails, triggering an AccessDenied error. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how KMS key policies interact with service-to-service encryption workflows, and it’s a common trap where candidates assume Glue inherits S3’s permissions. Remember: Glue decrypts the key itself, not through S3, so `kms:ViaService` must include `glue.amazonaws.com` or be removed. Memory tip: “Glue goes direct, not via S3—check ViaService for the right service key.”
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and 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.
Refer to the exhibit. A data engineer is troubleshooting a permissions issue. The IAM role 'DataEngineerRole' is used by an AWS Glue job that needs to read data from an S3 bucket encrypted with a customer managed KMS key. The above key policy is attached to the KMS key. The Glue job fails with an AccessDenied error when trying to read the data. 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 key policy condition 'kms:ViaService' restricts KMS actions to only when they are made through S3, but AWS Glue calls KMS directly, not via S3.
The key policy includes a condition `kms:ViaService` that restricts KMS actions to only when they are made through the S3 service. However, AWS Glue does not call KMS via S3; it calls KMS directly to decrypt the S3 object's data key. Because the Glue job's KMS request does not originate from the S3 service, the condition fails, resulting in an 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 key policy requires requests to originate from a VPC endpoint, but the Glue job is not using one.
Why it's wrong here
The policy does not reference VPC endpoints; it references kms:ViaService.
✗
The key policy denies requests that are not using HTTPS, but the Glue job is using HTTPS.
Why it's wrong here
The Deny statement with SecureTransport=false would deny non-HTTPS; if HTTPS is used, it's allowed.
✓
The key policy condition 'kms:ViaService' restricts KMS actions to only when they are made through S3, but AWS Glue calls KMS directly, not via S3.
Why this is correct
Glue does not use S3 to make KMS calls; it calls KMS directly, so the condition fails.
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 Glue job is running in a different AWS region than the S3 bucket.
Why it's wrong here
The kms:ViaService condition restricts the AWS service making the request, not the caller's region.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the nuance that `kms:ViaService` only applies when the KMS API call is made through the specified service's endpoint, not when a service like Glue calls KMS directly to decrypt an S3 object's key.
Detailed technical explanation
How to think about this question
The `kms:ViaService` condition key allows you to restrict KMS actions to requests that originate from a specific AWS service (e.g., `s3.amazonaws.com`). When AWS Glue reads an S3 object encrypted with SSE-KMS, it first calls KMS directly (not via S3) to decrypt the data key. This direct call does not satisfy the `kms:ViaService` condition, causing the policy to deny the request. In contrast, if the Glue job used an S3 VPC endpoint or if the key policy allowed direct KMS calls from the Glue job's IAM role, the access would succeed.
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.
Data Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The key policy condition 'kms:ViaService' restricts KMS actions to only when they are made through S3, but AWS Glue calls KMS directly, not via S3. — The key policy includes a condition `kms:ViaService` that restricts KMS actions to only when they are made through the S3 service. However, AWS Glue does not call KMS via S3; it calls KMS directly to decrypt the S3 object's data key. Because the Glue job's KMS request does not originate from the S3 service, the condition fails, resulting in an AccessDenied error.
What should I do if I get this DEA-C01 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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