MLS-C01 Data Engineering Practice Question
A company wants to store semi-structured data from IoT sensors in a cost-effective manner for occasional querying. The data is not updated once written. Which Amazon S3 storage class is the most cost-effective for this use case?
⚠ Common exam trap
A common mix-up: candidates choose S3 One Zone-Infrequent Access (Option B) because they focus on 'cost-effective' and 'infrequent access' without considering the requirement for durability and the even lower cost of Glacier Deep Archive for immutable archival data.
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
✓
S3 Glacier Deep Archive
S3 Glacier Deep Archive is the most cost-effective storage class for semi-structured IoT sensor data that is written once and only occasionally queried. It offers the lowest storage cost among S3 classes (approximately $0.00099/GB/month), making it ideal for long-term archival of immutable data where retrieval times of 12–48 hours are acceptable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
S3 Standard
Why it's wrong here
Incorrect: Standard is for frequently accessed data.
- ✗
S3 One Zone-Infrequent Access
Why it's wrong here
Incorrect: One Zone-IA is cheaper than Standard but still not the cheapest.
- ✗
S3 Intelligent-Tiering
Why it's wrong here
Incorrect: Intelligent-Tiering is good for unknown patterns but has a monitoring fee.
- ✓
S3 Glacier Deep Archive
Why this is correct
Correct: Deep Archive is the lowest cost for rarely accessed data with long retrieval times.
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 |
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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.