DEA-C01 Data Store Management Practice Question
A company runs an Apache Spark job on Amazon EMR that writes output to an S3 bucket. The job fails with the error 'S3AccessDeniedException' when writing the final output, but earlier stages succeed. The EMR cluster uses a service role and an instance profile. The S3 bucket policy allows access from the VPC only. What is the MOST likely cause?
⚠ Common exam trap
Test-takers frequently assume the EMR service role (EMR_EC2_DefaultRole) is responsible for all S3 access, but in reality the instance profile (EC2 instance role) handles data plane operations, and the bucket policy's VPC condition is the key blocker when earlier stages succeed but final writes fail.
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 EMR cluster is not using a VPC endpoint for S3, so requests are denied by the bucket policy's VPC condition.
The bucket policy restricts access to requests originating from the VPC, typically using a condition like `aws:SourceVpc`. If the EMR cluster does not use a VPC endpoint for S3 (either Gateway or Interface endpoint), traffic from the cluster to S3 traverses the public internet and does not match the VPC condition, causing the `S3AccessDeniedException`. Earlier stages may succeed if they use cached data or different paths, but the final write fails because it hits the bucket policy check.
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 uses SSE-C encryption, and the EMR cluster does not have the encryption key.
Why it's wrong here
SSE-C would cause a different error (InvalidArgument), not AccessDenied.
- ✗
The EMR service role does not have permissions to write to the S3 bucket.
Why it's wrong here
The service role is used by EMR to manage resources; the actual data access uses the instance profile.
- ✓
The EMR cluster is not using a VPC endpoint for S3, so requests are denied by the bucket policy's VPC condition.
Why this is correct
The bucket policy restricts access to VPC, but since the Spark job runs on EMR, its requests originate from inside the VPC only if a VPC endpoint is used; otherwise, they come from public IPs.
- ✗
The S3 bucket is configured with 'Bucket owner enforced' setting for ACLs, and the EMR cluster's account is not the bucket owner.
Why it's wrong here
Bucket owner enforced affects ACLs, not IAM policy evaluation; access is still controlled by bucket policy.
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
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.