This MLS-C01 practice question tests your understanding of data engineering. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Refer to the exhibit. A CloudFormation template creates an S3 bucket. The data engineering team stores daily log files in this bucket and queries them using Amazon Athena. After 30 days, queries on logs older than 30 days start failing with 'Access Denied' errors. What is the MOST likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The lifecycle rule transitions objects to GLACIER after 30 days, making them inaccessible to Athena.
Amazon Athena reads data directly from S3 and does not support querying objects stored in the GLACIER storage class because GLACIER objects are not retrievable in real time. The lifecycle rule transitions objects to GLACIER after 30 days, so when Athena attempts to read those older objects, it receives 'Access Denied' errors because the objects are no longer in a queryable storage class.
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.
✓
The lifecycle rule transitions objects to GLACIER after 30 days, making them inaccessible to Athena.
Why this is correct
Athena cannot query GLACIER objects; they must be restored first.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The bucket uses default encryption with SSE-S3, which Athena does not support.
Why it's wrong here
Athena supports SSE-S3.
✗
The lifecycle rule deletes objects after 30 days.
Why it's wrong here
ExpirationInDays is 365, not 30.
✗
The bucket policy denies access to objects older than 30 days.
Why it's wrong here
No bucket policy is defined in the template.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'Access Denied' errors with permission issues (bucket policies or IAM) rather than recognizing that the error is caused by the storage class transition to GLACIER, which makes objects unreadable by Athena without restoration.
Detailed technical explanation
How to think about this question
When an S3 lifecycle rule transitions an object to GLACIER, the object's storage class changes, and the object becomes inaccessible for real-time reads until restored (which takes 3–5 hours). Athena uses S3 GET requests to read data, and S3 returns an 'Access Denied' error (HTTP 403) when attempting to GET an object in GLACIER without prior restoration, because the underlying data is not immediately available. This is a common pitfall when using Athena on S3 buckets with lifecycle policies that archive older data.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: The lifecycle rule transitions objects to GLACIER after 30 days, making them inaccessible to Athena. — Amazon Athena reads data directly from S3 and does not support querying objects stored in the GLACIER storage class because GLACIER objects are not retrievable in real time. The lifecycle rule transitions objects to GLACIER after 30 days, so when Athena attempts to read those older objects, it receives 'Access Denied' errors because the objects are no longer in a queryable storage class.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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