- A
S3 Standard
Why wrong: Incorrect: Standard is for frequently accessed data.
- B
S3 One Zone-Infrequent Access
Why wrong: Incorrect: One Zone-IA is cheaper than Standard but still not the cheapest.
- C
S3 Intelligent-Tiering
Why wrong: Incorrect: Intelligent-Tiering is good for unknown patterns but has a monitoring fee.
- D
S3 Glacier Deep Archive
Correct: Deep Archive is the lowest cost for rarely accessed data with long retrieval times.
Question 1,307 of 1,755
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often 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.
Detailed technical explanation
How to think about this question
S3 Glacier Deep Archive uses a separate, lower-cost storage infrastructure with retrieval times ranging from 12 to 48 hours via the 'Expedited' or 'Standard' retrieval options, and data is stored in multiple geographically separate facilities (at least three AZs) for 99.999999999% durability. A subtle behavior is that objects in this class are not immediately accessible via standard S3 GET requests; you must first initiate a restore job that copies the object to a temporary S3 Standard tier, which can incur retrieval costs if done frequently. In a real-world scenario, a company collecting temperature readings from thousands of sensors every minute might store raw data in Glacier Deep Archive for compliance, querying it only once a quarter for trend analysis.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 |
What to study next
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FAQ
Questions learners often ask
What does this MLS-C01 question test?
Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this MLS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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.
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