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MLS-C01 Data Engineering Practice Question

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.

Exhibit

Refer to the exhibit.

Resources:
  MyGlueJob:
    Type: AWS::Glue::Job
    Properties:
      Command:
        Name: glueetl
        ScriptLocation: s3://my-bucket/scripts/etl.py
      DefaultArguments:
        --TempDir: s3://my-bucket/temp/
        --job-bookmark-option: job-bookmark-enable
      MaxRetries: 0
      MaxConcurrentRuns: 3
      Role: arn:aws:iam::123456789012:role/GlueServiceRole

A company uses AWS Glue jobs with job bookmarks enabled to process incremental data. They notice that the job processes all data each time instead of only new data. 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.

Exhibit

Refer to the exhibit.

Resources:
  MyGlueJob:
    Type: AWS::Glue::Job
    Properties:
      Command:
        Name: glueetl
        ScriptLocation: s3://my-bucket/scripts/etl.py
      DefaultArguments:
        --TempDir: s3://my-bucket/temp/
        --job-bookmark-option: job-bookmark-enable
      MaxRetries: 0
      MaxConcurrentRuns: 3
      Role: arn:aws:iam::123456789012:role/GlueServiceRole

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 MaxConcurrentRuns is set to 3, which can cause bookmark conflicts.

Option D is correct because setting MaxConcurrentRuns to a value greater than 1 can cause job bookmark conflicts. When multiple concurrent runs of the same AWS Glue job attempt to update the bookmark state simultaneously, they can overwrite each other's progress, leading to inconsistent bookmark tracking. This results in the job reprocessing all data instead of only incremental data, as the bookmark fails to correctly record the last processed position.

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 TempDir is not configured correctly.

    Why it's wrong here

    TempDir is for temporary files, not bookmarks.

  • ✗

    The job bookmark option is set to 'job-bookmark-enable' but should be 'job-bookmark-disable'.

    Why it's wrong here

    Enabling is correct for incremental processing.

  • ✗

    The source data does not have a column that can be used as a bookmark key.

    Why it's wrong here

    While true, the more direct cause is concurrent runs.

  • ✓

    The MaxConcurrentRuns is set to 3, which can cause bookmark conflicts.

    Why this is correct

    Multiple concurrent runs can corrupt bookmark state.

    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.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often overlook the impact of concurrent runs on bookmark state, assuming that parallelism only affects performance, not data integrity, and instead focus on superficial configuration issues like TempDir or bookmark key columns.

Detailed technical explanation

How to think about this question

AWS Glue job bookmarks rely on a state file stored in the TempDir (or a dedicated bookmark location) to track the last processed data. When MaxConcurrentRuns > 1, multiple Spark executors may attempt to write to this state file concurrently, causing race conditions that corrupt the bookmark state. In practice, this is a common misconfiguration when users enable parallel job runs for performance without understanding that bookmarks require sequential execution to maintain consistency.

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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.

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.

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FAQ

Questions learners often ask

What does this MLS-C01 question test?

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 MaxConcurrentRuns is set to 3, which can cause bookmark conflicts. — Option D is correct because setting MaxConcurrentRuns to a value greater than 1 can cause job bookmark conflicts. When multiple concurrent runs of the same AWS Glue job attempt to update the bookmark state simultaneously, they can overwrite each other's progress, leading to inconsistent bookmark tracking. This results in the job reprocessing all data instead of only incremental data, as the bookmark fails to correctly record the last processed position.

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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Last reviewed: Jul 4, 2026

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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.