DEA-C01 Data Ingestion and Transformation Practice Question
A data engineer needs to load data from an on-premises Oracle database to Amazon S3 daily. The table is 500 GB and grows by 50 MB per day. The load must capture only new and changed rows since the last run. Which solution is MOST cost-effective and requires the least maintenance?
⚠ Common exam trap
Candidates often choose AWS Glue with a timestamp filter (Option C) because it seems simpler, but they overlook that Glue still performs a full table scan via JDBC to apply the filter, which is inefficient for large tables and does not provide true CDC from redo logs, unlike DMS's native log-based replication.
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 AWS Database Migration Service (DMS) with ongoing replication (CDC)
AWS DMS with ongoing replication (CDC) is the most cost-effective and low-maintenance solution because it continuously captures only new and changed rows from the Oracle source using its built-in CDC mechanism (reading redo logs), without requiring custom scripting or full table exports. It automatically handles schema changes, resumability, and incremental loading to S3, minimizing operational overhead and data transfer costs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Write a custom Python script on EC2 to query the Oracle redo logs and upload to S3
Why it's wrong here
Custom scripts require ongoing maintenance and error handling.
- ✗
Export the entire table to CSV daily using a script and upload to S3
Why it's wrong here
Full export daily is inefficient and costly for large tables.
- ✗
Use AWS Glue ETL job with a JDBC connection and a timestamp filter
Why it's wrong here
Glue does not have built-in CDC; timestamp-based filtering may miss updates or deletes.
- ✓
Use AWS Database Migration Service (DMS) with ongoing replication (CDC)
Why this is correct
DMS supports CDC and can capture only changes, minimizing cost and effort.
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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