The answer is an S3 event notification invoking a Lambda function, as this serverless approach is the most cost-effective and requires the least maintenance for a cost-effective CSV to Parquet transformation using S3 Lambda. Lambda executes only when a file lands, with no idle cost, and scales automatically, whereas AWS Glue jobs incur a minimum one-minute billing per invocation, making them pricier for sporadic uploads. On the MLS-C01 exam, this scenario tests your understanding of serverless data processing trade-offs; a common trap is choosing Glue for its ETL features, but the question emphasizes cost and maintenance over complexity. Remember, for lightweight, event-driven transformations, Lambda wins—Glue is for heavy lifting, EMR for clusters. Memory tip: “Lambda lands, Parquet expands—no idle hands, no billing bands.”
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 needs to automate the transformation of CSV files to Parquet format as soon as they are uploaded to an S3 bucket. The transformed files should be stored in another S3 bucket. Which solution is the most cost-effective and requires the least maintenance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure an S3 event notification to invoke a Lambda function.
S3 Event Notification to Lambda is serverless and cost-effective. Glue jobs have a minimum billing of 1 minute. EMR is overkill. EC2 requires management.
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.
✓
Configure an S3 event notification to invoke a Lambda function.
Why this is correct
Lambda is serverless, pay-per-execution, ideal for this use case.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure an S3 event notification to invoke an AWS Glue job.
Why it's wrong here
Glue has a minimum billing and is less cost-effective for small transformations.
✗
Run an Amazon EMR cluster continuously to watch for new files.
Why it's wrong here
EMR is expensive and high maintenance.
✗
Set up an EC2 instance with a cron job to poll the S3 bucket.
Why it's wrong here
EC2 requires management and is not cost-effective.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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.
What to study next
Got this wrong? Here's your next step.
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Configure an S3 event notification to invoke a Lambda function. — S3 Event Notification to Lambda is serverless and cost-effective. Glue jobs have a minimum billing of 1 minute. EMR is overkill. EC2 requires management.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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.
Question Discussion
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