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.
A data engineer uses the IAM policy above for an AWS Lambda function that processes data in S3 and triggers an AWS Glue job. The Lambda function is unable to start the Glue job. What is the most likely cause?
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 policy does not include iam:PassRole permission.
The Lambda function needs to pass an IAM role to AWS Glue when starting a job, which requires the `iam:PassRole` permission. Without this permission, the `StartJobRun` API call fails even if the Lambda has permissions to invoke Glue. The policy shown lacks this critical permission, making option C the correct answer.
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 Glue job name in the resource ARN is misspelled.
Why it's wrong here
The exhibit does not indicate misspelling.
✗
The policy does not allow s3:PutObject on the bucket.
Why it's wrong here
The policy includes s3:PutObject.
✓
The policy does not include iam:PassRole permission.
Why this is correct
To start a Glue job, Lambda must pass an execution role; iam:PassRole is required.
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 policy does not include s3:GetObject on the bucket.
Why it's wrong here
The policy includes s3:GetObject on the bucket.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates focus on S3 permissions (options B and D) because the Lambda processes S3 data, but the actual failure is the missing IAM permission required to delegate a role to AWS Glue, which is a subtle but critical detail in cross-service orchestration.
Detailed technical explanation
How to think about this question
The `iam:PassRole` permission is required when a service (like AWS Glue) assumes a role on behalf of the caller (the Lambda function). This is enforced via the `PassRole` action in IAM, and the role ARN must match the resource in the policy. In practice, this is a common oversight when setting up cross-service workflows, as the Lambda execution role must explicitly allow passing the Glue service role.
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 policy does not include iam:PassRole permission. — The Lambda function needs to pass an IAM role to AWS Glue when starting a job, which requires the `iam:PassRole` permission. Without this permission, the `StartJobRun` API call fails even if the Lambda has permissions to invoke Glue. The policy shown lacks this critical permission, making option C the correct answer.
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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