MLS-C01 Data Engineering Practice Question
Exhibit
Refer to the exhibit.
{
"RoleName": "MLDataProcessingRole",
"AssumeRolePolicyDocument": {
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": "glue.amazonaws.com"
},
"Action": "sts:AssumeRole"
}
]
},
"AttachedManagedPolicies": [
"arn:aws:iam::aws:policy/AmazonS3FullAccess",
"arn:aws:iam::aws:policy/AWSGlueServiceRole"
]
}An AWS Glue job is failing with an error that it cannot access an S3 bucket. The IAM role attached to the Glue job is shown in the exhibit. What is the MOST likely cause of the failure?
⚠ Common exam trap
Many exam-takers assume the IAM role's permissions are the only factor, ignoring that S3 bucket policies can independently deny access, which overrides any allow in the role's 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 S3 bucket has a bucket policy that denies access to this role
Even if the IAM role has S3 permissions, an S3 bucket policy that explicitly denies access to that role will override any allow. AWS evaluates all policies (identity-based and resource-based) and a deny in any policy results in a final deny decision. The error indicates the Glue job cannot access the bucket, which is consistent with a bucket-level deny.
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 has a bucket policy that denies access to this role
Why this is correct
A bucket policy can override the role's permissions.
- ✗
The role lacks S3 permissions
Why it's wrong here
The role has AmazonS3FullAccess attached.
- ✗
The role does not have permission to call S3 APIs
Why it's wrong here
AmazonS3FullAccess grants all S3 actions.
- ✗
The trust policy does not allow Glue to assume the role
Why it's wrong here
The trust policy explicitly allows glue.amazonaws.com.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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