DEA-C01 Data Ingestion and Transformation Practice Question
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?
⚠ Common exam trap
Many candidates 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.
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 crawler is configured to only add new partitions to existing tables, but the table schema has changed.
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.
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.
- ✗
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.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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