MLS-C01 Practice Question: Machine Learning Implementation and Operations
A company is using Amazon SageMaker to train a model. The training data is stored in an S3 bucket encrypted with AWS KMS. The SageMaker training role has the necessary permissions to decrypt the data. However, the training job fails with an access denied error. What is the most likely cause?
⚠ Common exam trap
The MLS-C01 exam often tests the misconception that S3 bucket policies alone control access to encrypted data, but the trap here is that KMS decryption permissions are a separate, required layer — candidates may overlook the need for kms:Decrypt when the role already has s3:GetObject.
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 training role does not have kms:Decrypt permission for the KMS key
The error message 'access denied' during a SageMaker training job with KMS-encrypted S3 data typically indicates that the training role lacks the kms:Decrypt permission for the specific KMS key used to encrypt the S3 objects. Even if the role has S3 read permissions (s3:GetObject), SageMaker must decrypt the data before reading it, which requires explicit KMS key policy or IAM policy granting kms:Decrypt. Without this, the training job fails with an access denied error.
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 S3 bucket policy does not grant access to the training role
Why it's wrong here
The role has S3 access, but KMS is separate.
- ✗
The training image is not compatible with encrypted data
Why it's wrong here
Training images can read encrypted data with proper permissions.
- ✓
The training role does not have kms:Decrypt permission for the KMS key
Why this is correct
KMS requires explicit decrypt permission.
- ✗
CloudTrail logging is disabled
Why it's wrong here
CloudTrail does not affect access.
- ✗
The training job is not in the same VPC as the S3 bucket
Why it's wrong here
VPC is not required for S3 access.
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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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This MLS-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 MLS-C01 exam.