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. An IAM policy is attached to a data engineering role. The role is used by an AWS Glue ETL job that reads from 'raw/' and writes to 'processed/'. The job fails with an access denied error when trying to write to 'processed/'. What is the likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Deny statement on s3:DeleteObject prevents overwriting objects.
Option A is correct because the Deny statement on s3:DeleteObject explicitly denies the permission required to overwrite an existing object in S3. When an AWS Glue job writes to 'processed/' and attempts to overwrite an existing object, S3 requires both s3:PutObject and s3:DeleteObject permissions (since overwrite involves delete then put). The Deny on DeleteObject causes the access denied error. Option B is incorrect because the role is presumed to be attached correctly per the scenario. Option C is incorrect because the policy allows both GetObject and PutObject on the same resource, as is typical. Option D is incorrect because the ARN for the 'processed' folder is correctly specified; the error is due to the Deny, not incorrect ARN.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 Deny statement on s3:DeleteObject prevents overwriting objects.
Why this is correct
If the job tries to overwrite an existing object, it needs DeleteObject permission.
Related concept
Standard ACLs match source addresses.
✗
The role is not correctly attached to the Glue job.
Why it's wrong here
Assume attachment is correct.
✗
The policy does not allow both s3:GetObject and s3:PutObject on the same resource.
Why it's wrong here
The policy allows both on separate resources.
✗
The policy specifies incorrect ARN for the 'processed' folder.
Why it's wrong here
The ARN is correctly specified.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related MLS-C01 ACL questions on filtering logic and placement.
Data Engineering — This question tests Data Engineering — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The Deny statement on s3:DeleteObject prevents overwriting objects. — Option A is correct because the Deny statement on s3:DeleteObject explicitly denies the permission required to overwrite an existing object in S3. When an AWS Glue job writes to 'processed/' and attempts to overwrite an existing object, S3 requires both s3:PutObject and s3:DeleteObject permissions (since overwrite involves delete then put). The Deny on DeleteObject causes the access denied error. Option B is incorrect because the role is presumed to be attached correctly per the scenario. Option C is incorrect because the policy allows both GetObject and PutObject on the same resource, as is typical. Option D is incorrect because the ARN for the 'processed' folder is correctly specified; the error is due to the Deny, not incorrect ARN.
What should I do if I get this MLS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related MLS-C01 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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