The answer is that the crawler is configured to only add new partitions to existing tables, but the table schema has changed. This is correct because AWS Glue Crawlers, by default, use a "Add new partitions only" update behavior, which prevents them from detecting new partitions if the underlying data schema has drifted—such as when new columns or different data types appear in the newly added S3 partitions. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how Glue Crawlers handle schema evolution and partition discovery, a common trap being that candidates assume any new partition will always be added. A key memory tip: think of the crawler as "schema-loyal"—it refuses new partitions if the schema looks different, so always check the crawler’s "Update the table definition" option if you expect schema changes.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 uses AWS Glue to catalog data from an S3 bucket. The data is partitioned by year, month, day. After adding new partitions, the Glue Crawler does not detect them. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The crawler is configured to only add new partitions to existing tables, but the table schema has changed.
Option A is correct because the Glue Crawler, by default, is configured to add new partitions only if the table schema remains unchanged. When new partitions are added to an S3 bucket, if the underlying data schema has changed (e.g., new columns, different data types), the crawler will not add those partitions to the existing table. This is a common safeguard to prevent schema drift from corrupting the cataloged table structure.
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 crawler is configured to only add new partitions to existing tables, but the table schema has changed.
Why this is correct
If the schema changed, the crawler may skip partitions; or if the crawler is set to not update new partitions, it won't add them.
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.
✗
The crawler runs only once and does not schedule subsequent runs.
Why it's wrong here
Even if scheduled, the crawler may not detect partitions if configuration is wrong.
✗
The IAM role lacks permission to write to the Glue Data Catalog.
Why it's wrong here
Lack of write permission would cause the crawler to fail with an error.
✗
The partition depth exceeds the crawler's default limit.
Why it's wrong here
Glue Crawler supports up to 10 partition levels; year/month/day is 3 levels.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume partition detection failures are due to permissions or depth limits, but AWS Glue's default schema-change protection is the subtle and less obvious cause.
Detailed technical explanation
How to think about this question
Under the hood, the Glue Crawler uses a classifier to infer schema and then compares it to the existing table's schema in the Data Catalog. If the schemas differ, the crawler's default behavior is to skip adding new partitions to avoid schema inconsistency. This behavior can be overridden by enabling 'Update all new and existing partitions with metadata from the table' in the crawler configuration, which forces schema updates. In real-world scenarios, this often catches data engineers off guard when they add a new column to Parquet files and wonder why partitions aren't appearing.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 is configured to only add new partitions to existing tables, but the table schema has changed. — Option A is correct because the Glue Crawler, by default, is configured to add new partitions only if the table schema remains unchanged. When new partitions are added to an S3 bucket, if the underlying data schema has changed (e.g., new columns, different data types), the crawler will not add those partitions to the existing table. This is a common safeguard to prevent schema drift from corrupting the cataloged table structure.
What should I do if I get this DEA-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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Question Discussion
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