DEA-C01 KMS Key Policy Practice Question
A data engineer is troubleshooting an issue where an AWS Glue ETL job fails when trying to read data from an S3 bucket encrypted with SSE-KMS. The job has an IAM role that includes `kms:Decrypt` permission. What is the most likely reason for the failure?
⚠ Common exam trap
DEA-C01 often tests the dual requirement of IAM policies and KMS key policies for accessing encrypted data, and candidates may overlook the key policy.
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 KMS key policy does not allow the Glue job to use the key
Even if the IAM role has `kms:Decrypt` permission, the KMS key policy must also allow the Glue job's role to use the key. KMS key policies are resource-based policies that control access to the key, and if they do not explicitly grant permission to the Glue job's role, the decrypt operation will fail. This is a common oversight when using SSE-KMS with services like AWS Glue.
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 IAM role does not have s3:GetObject permission
Why it's wrong here
Without s3:GetObject the job cannot read the object at all, but the stem states the failure is KMS-related and the role already holds kms:Decrypt. It is tempting because missing S3 permissions commonly break Glue jobs, yet the described symptom points to the KMS key policy instead.
- ✓
The KMS key policy does not allow the Glue job to use the key
Why this is correct
Correct. The most likely cause is that the KMS key policy does not grant the Glue job's IAM role permission to use the key. Even with kms:Decrypt in the role, the key policy must allow it.
- ✗
The S3 bucket is in a different AWS region than the Glue job
Why it's wrong here
Cross-region S3 access is supported and does not cause KMS decryption failures; the KMS key policy, not region, governs access. Region mismatch is tempting because latency and data-transfer concerns are real, but the actual blocker is the key policy denying the Glue role.
- ✗
The Glue job is not configured to use the KMS key for decryption
Why it's wrong here
Incorrect. AWS Glue does not require explicit configuration of the KMS key to read SSE-KMS encrypted data; the decryption is handled automatically when the job role has adequate KMS permissions and the key policy allows it.
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 |
Go deeper
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This DEA-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 DEA-C01 exam.