The answer is a custom classifier that defines a fixed schema. When an AWS Glue crawler is configured with a custom classifier that explicitly maps columns to a rigid structure, it will ignore any new columns added to CSV files because the classifier’s schema takes precedence over schema inference from the data. This is a common cause of AWS Glue crawler schema update failure, as the crawler does not automatically detect or incorporate changes outside the defined schema. On the AWS Certified Data Engineer Associate DEA-C01 exam, this concept tests your understanding of how custom classifiers override default schema discovery behavior—a frequent trap where candidates assume the crawler always adapts to new columns. Remember, partition discovery and S3 event notifications do not affect schema updates, and IAM permission issues would produce a different error entirely. Memory tip: “Fixed classifier, fixed schema—new columns get the cold shoulder.”
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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 company uses AWS Glue crawlers to populate the Data Catalog from data in Amazon S3. The crawler fails to update the schema when new columns are added to the CSV files. 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 crawler uses a custom classifier that defines a fixed schema.
Option A is correct because if the crawler is configured with a custom classifier that expects a fixed schema, it will ignore new columns. Option B is wrong because partition discovery does not prevent schema updates. Option C is wrong because S3 event notifications are not related. Option D is wrong because IAM permissions would cause a different error.
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 S3 bucket has versioning enabled.
Why it's wrong here
Versioning does not affect crawler behavior.
✗
The crawler is configured to only crawl new partitions.
Why it's wrong here
Partition discovery does not affect schema update.
✗
The IAM role for the crawler lacks permissions to read the new columns.
Why it's wrong here
Permissions would cause access errors, not ignored columns.
✓
The crawler uses a custom classifier that defines a fixed schema.
Why this is correct
Custom classifiers can override schema inference.
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
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 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.
What to study next
Got this wrong? Here's your next step.
Identify which DEA-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 Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The crawler uses a custom classifier that defines a fixed schema. — Option A is correct because if the crawler is configured with a custom classifier that expects a fixed schema, it will ignore new columns. Option B is wrong because partition discovery does not prevent schema updates. Option C is wrong because S3 event notifications are not related. Option D is wrong because IAM permissions would cause a different error.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-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: "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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This DEA-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 DEA-C01 exam.
Question Discussion
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