The answer is that the crawler configuration has 'Update the table definition' set to 'Ignore the change'. This is the most likely cause of an AWS Glue crawler schema update failure because when new columns are added to Parquet data in Amazon S3, the crawler will not modify the table definition in the Data Catalog unless its catalog update policy explicitly allows schema evolution. Parquet format inherently supports schema evolution, so the issue is not with the file format but with the crawler's configuration preventing it from detecting and applying the new columns. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Glue crawler behavior versus schema compatibility—a common trap is assuming Parquet or S3 versioning causes the failure, when the real culprit is the crawler’s update policy. Remember the memory tip: "Ignore the change, ignore the column" to recall that setting the policy to ignore prevents any schema updates.
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 to catalog data in Amazon S3. The data arrives in Parquet format, but the crawler fails to update the schema when new columns are added. 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 configuration has 'Update the table definition' set to 'Ignore the change'.
Option C is correct because the crawler's catalog update policy may be set to 'Update the table definition' but not 'Add new columns only', or it might be set to 'Ignore the change'. Option A is wrong because Parquet schema evolves naturally. Option B is wrong because S3 bucket versioning does not affect crawler schema updates. Option D is wrong because the Glue Data Catalog is the target, not the source.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 Data Catalog is not configured to accept schema changes.
Why it's wrong here
The Data Catalog accepts changes; the crawler configuration controls them.
✗
Parquet files do not support schema evolution.
Why it's wrong here
Parquet supports schema evolution; new columns can be added.
✓
The crawler configuration has 'Update the table definition' set to 'Ignore the change'.
Why this is correct
If set to ignore changes, the crawler will not add new columns.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The S3 bucket has versioning disabled.
Why it's wrong here
S3 versioning is unrelated to Glue crawler schema detection.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The crawler configuration has 'Update the table definition' set to 'Ignore the change'. — Option C is correct because the crawler's catalog update policy may be set to 'Update the table definition' but not 'Add new columns only', or it might be set to 'Ignore the change'. Option A is wrong because Parquet schema evolves naturally. Option B is wrong because S3 bucket versioning does not affect crawler schema updates. Option D is wrong because the Glue Data Catalog is the target, not the source.
What should I do if I get this DEA-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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Question Discussion
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