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AIF-C01 Practice Question: A machine learning engineer notices that a…
A machine learning engineer notices that a SageMaker training job failed due to insufficient permissions to access a KMS-encrypted S3 bucket. The training job's IAM role has S3 access permissions. What should be done to resolve the issue?
⚠ Common exam trap
Watch out — candidates often assume S3 permissions alone are sufficient, overlooking that KMS-encrypted objects require explicit kms:Decrypt permissions on the IAM role, not just S3 bucket policies or managed policies like SageMakerFullAccess.
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
✓
Add a kms:Decrypt permission to the IAM role for the specific KMS key used to encrypt the S3 bucket
The training job failed because the IAM role lacks permission to decrypt the KMS key used for S3 server-side encryption. Even with S3 access permissions, SageMaker cannot read encrypted objects without the kms:Decrypt action on the specific KMS key. Adding kms:Decrypt to the role's policy for that key resolves the issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a new KMS key and re-encrypt the data
Why it's wrong here
Creating and re-encrypting with a new key does not grant the training role kms:Decrypt on that key, so access still fails. It is tempting because key management appears to be the problem, and would be correct if the existing key were compromised or needed rotation.
- ✗
Assign the SageMakerFullAccess policy to the role
Why it's wrong here
SageMakerFullAccess grants broad SageMaker and S3 permissions but no kms:Decrypt, so the role still cannot read KMS-encrypted objects. It is tempting as a catch-all fix for permission errors, and would be correct when a role genuinely lacks SageMaker service permissions rather than key access.
- ✓
Add a kms:Decrypt permission to the IAM role for the specific KMS key used to encrypt the S3 bucket
Why this is correct
S3 access alone cannot decrypt KMS-encrypted objects; the training job's IAM role also needs kms:Decrypt on the specific key. This satisfies the stem's constraint that S3 permissions already exist, isolating the missing key-level authorisation as the cause of failure.
- ✗
Change the S3 bucket's default encryption to S3-managed keys (SSE-S3)
Why it's wrong here
Switching to SSE-S3 removes KMS encryption entirely, altering the bucket's security posture instead of granting the role kms:Decrypt on the existing key. It is tempting because it sidesteps the permission error, and would be correct if the requirement were to avoid customer-managed keys rather than retain KMS encryption.
Visual reference
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 |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AIF-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 AIF-C01 exam.