DEA-C01 Data Ingestion and Transformation Practice Question
A data engineer is using AWS Glue DataBrew to clean a dataset stored in Amazon S3. The dataset contains inconsistent date formats in a column named 'transaction_date'. The engineer needs to standardize all dates to ISO 8601 format (YYYY-MM-DD) and then write the cleaned data to a new S3 location. Which transformation should the engineer apply?
⚠ Common exam trap
Many exam-takers confuse data type conversion with date formatting; changing the type does not reformat the string, and simple string replacements cannot handle varying date orders.
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
✓
Use the 'Format date' transformation with a custom date format pattern.
The 'Format date' transformation in AWS Glue DataBrew is designed to parse and reformat date values. By specifying the input format(s) and setting the output format to 'yyyy-MM-dd', the engineer can standardize inconsistent date strings into ISO 8601. This ensures consistency for downstream processing and analytics, and it handles multiple input patterns without manual string manipulation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use the 'Change data type' transformation to convert the column to a date type.
Why it's wrong here
Changing the data type to date does not standardize the format; it only interprets the existing values. If the source has multiple formats, the conversion may fail or produce nulls. The requirement is to standardize the format to ISO 8601, which requires parsing and reformatting, not just a type change.
- ✗
Use the 'Replace value' transformation to replace all date separators with hyphens.
Why it's wrong here
Replacing separators does not account for different date orders (e.g., MM/DD/YYYY vs DD-MM-YYYY). It could produce incorrect dates, such as swapping month and day. This approach is error-prone and does not guarantee ISO 8601 compliance, especially with mixed formats.
- ✓
Use the 'Format date' transformation with a custom date format pattern.
Why this is correct
The 'Format date' transformation in AWS Glue DataBrew allows specifying input and output date formats. By setting the output format to 'yyyy-MM-dd', the engineer can standardize all dates to ISO 8601. This transformation handles multiple input formats if configured correctly, making it the appropriate choice for this scenario.
- ✗
Use the 'Split column' transformation to separate day, month, and year into individual columns.
Why it's wrong here
Splitting the column creates three separate columns, which does not produce a single standardized date column. The requirement is to standardize the 'transaction_date' column to ISO 8601 format, not to decompose it. This would require additional transformations to reassemble, adding unnecessary complexity.
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 |
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.