MLS-C01 Practice Question: Machine Learning Implementation and Operations

Exhibit

Refer to the exhibit.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["s3:GetObject"],
      "Resource": "arn:aws:s3:::my-bucket/*"
    },
    {
      "Effect": "Allow",
      "Action": ["sagemaker:CreateTrainingJob"],
      "Resource": "*"
    }
  ]
}

A data scientist is trying to create a SageMaker training job using an execution role with the attached IAM policy. The training job fails with an access denied error when trying to read training data from the S3 bucket 'my-bucket'. What is the most likely cause?

⚠ Common exam trap

Many candidates assume the IAM policy is insufficient (e.g., missing ListBucket) or that cross-account issues are the cause, but the most likely cause is an explicit deny in the bucket policy, which is a classic AWS IAM evaluation logic trick.

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 S3 bucket policy explicitly denies access to the role.

The most likely cause is that the S3 bucket policy explicitly denies access to the SageMaker execution role. Even if the IAM policy grants the necessary permissions, an explicit deny in the bucket policy overrides any allow, resulting in an access denied error when the training job attempts to read training data from the S3 bucket.

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 explicitly denies access to the role.
Why this is correct
Even if IAM allows, bucket policy can deny.
✗
The IAM policy does not include s3:ListBucket permission.
Why it's wrong here
GetObject does not require ListBucket.
✗
The S3 bucket is in a different AWS account.
Why it's wrong here
Cross-account access would need bucket policy, but access denied could be due to bucket policy.
✗
The sagemaker:CreateTrainingJob action is not allowed.
Why it's wrong here
It is allowed with Resource: "*".

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

MLS-C01 Practice Question: Machine Learning Implementation and Operations

Exhibit

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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