MLS-C01 Data Engineering Practice Question
A company is building a data lake on Amazon S3. They need to enforce encryption at rest for all objects. Which combination of actions will achieve this? (Assume the bucket is versioned.)
⚠ Common exam trap
A common mix-up: candidates assume S3 default encryption alone is sufficient, but the exam tests the nuance that default encryption can be overridden by client-supplied headers, requiring a bucket policy to enforce encryption for all PutObject requests.
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
✓
Enable S3 default encryption and set a bucket policy to deny PutObject without encryption headers
Combining S3 default encryption with a bucket policy that denies PutObject requests lacking encryption headers ensures that every object stored in the bucket is encrypted at rest, even if the PutObject call does not include encryption parameters. Default encryption alone can be overridden by a client that explicitly sets encryption headers, but the bucket policy enforces encryption for all uploads, closing that loophole. This dual approach guarantees compliance with encryption-at-rest requirements for a versioned 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.
- ✗
Use AWS KMS with automatic key rotation
Why it's wrong here
This manages keys but does not enforce encryption.
- ✓
Enable S3 default encryption and set a bucket policy to deny PutObject without encryption headers
Why this is correct
This ensures all objects are encrypted.
- ✗
Enable S3 default encryption only
Why it's wrong here
Default encryption does not prevent clients from overriding with no encryption.
- ✗
Enable S3 Block Public Access
Why it's wrong here
This prevents public access, not encryption.
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
Related to this question
About these practice questions
One of 1,672 original MLS-C01 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.