MLS-C01 Data Engineering Practice Question
Network Topology
Refer to the exhibit. A data engineer runs the AWS CLI command to check an object in an S3 bucket. The bucket is part of a data lake and is configured with versioning enabled. However, the output shows "VersionId": null. What is the most likely reason for this?
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 object was uploaded before versioning was enabled
The most likely reason is that the object was uploaded before versioning was enabled on the bucket. When versioning is enabled, objects uploaded afterward receive a unique version ID, while objects that existed before versioning was enabled have a null version ID. Option B is correct. Option A is incorrect because SSE-S3 encryption does not affect version IDs; version IDs are metadata independent of encryption. Option C is incorrect because the `head-object` command automatically returns the version ID of the latest version; no `--version-id` parameter is needed to display it. Option D is incorrect because the bucket is explicitly stated to have versioning enabled.
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 object is encrypted using SSE-S3, which hides the version ID
Why it's wrong here
Encryption does not affect version ID visibility.
- ✓
The object was uploaded before versioning was enabled
Why this is correct
Objects uploaded before versioning was enabled have a null version ID.
- ✗
The command must include the --version-id parameter to display the version ID
Why it's wrong here
Even without --version-id, the latest version's version ID is shown if versioning is enabled.
- ✗
Versioning is not enabled on the bucket
Why it's wrong here
The stem says versioning is enabled.
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 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.