MLS-C01 Data Engineering Practice Question
Network Topology
A data engineer runs the AWS CLI command shown and notices a zero-byte file in the results. What is the most likely cause of this zero-byte file?
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
✓
The file was created by a failed Spark task that wrote no data.
Zero-byte files often occur when an ETL job fails partway through writing, or when a task starts but writes no data. A completed write would have non-zero size. The other options are less likely: prefix typo wouldn't produce a file; correct permissions wouldn't cause zero bytes; compression would produce some output.
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 S3 bucket has a lifecycle policy that deleted the content.
Why it's wrong here
Lifecycle policies delete objects, not content.
- ✗
The file was written with the wrong prefix.
Why it's wrong here
Wrong prefix would not affect file content.
- ✗
The file was compressed, reducing size to zero.
Why it's wrong here
Compression reduces size but not to zero.
- ✓
The file was created by a failed Spark task that wrote no data.
Why this is correct
Failed tasks can produce empty files.
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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.