DEA-C01 Data Ingestion and Transformation Practice Question
A data engineering team needs to transform CSV files to Parquet format after they land in an S3 bucket. The transformation should be triggered automatically as soon as a new file arrives. Which AWS service is best suited for this task?
⚠ Common exam trap
Many candidates choose AWS Glue (Option D) because it is a dedicated ETL service, but they overlook the requirement for immediate, event-driven processing, which Glue's scheduled jobs cannot provide without additional event-bridge triggers.
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
✓
AWS Lambda function triggered by S3 event
AWS Lambda functions can be directly triggered by S3 events (e.g., `s3:ObjectCreated:*`) to process newly uploaded CSV files. This serverless approach provides near-instantaneous, event-driven transformation to Parquet without managing any infrastructure, making it the most cost-effective and simplest solution for this specific use case.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AWS Batch job submitted by S3 event
Why it's wrong here
AWS Batch runs containerised compute jobs but has no native S3 event integration; an S3 notification would need to invoke Lambda to submit the job, adding orchestration. Batch suits long-running or queued compute workloads. The stem's requirement is direct, automatic transformation on arrival, which Batch does not provide by itself.
- ✗
Amazon EMR cluster running continuously
Why it's wrong here
A continuously running EMR cluster bills for idle capacity between arrivals and does not itself react to S3 events; it needs polling or step submission. EMR suits sustained, heavy Spark or Hadoop workloads. Here the requirement is event-driven, near-immediate transformation of individual files, which an always-on cluster neither triggers nor costs efficiently for.
- ✓
AWS Lambda function triggered by S3 event
Why this is correct
S3 event notifications invoke a Lambda function within milliseconds of each object landing, satisfying the immediate-trigger requirement. Lambda natively transforms CSV to Parquet using libraries such as pandas with pyarrow, writing output back to S3, with no cluster provisioning or polling needed for this short, event-driven task.
- ✗
AWS Glue ETL job scheduled every 5 minutes
Why it's wrong here
A five-minute schedule introduces latency and processes arrivals in batches rather than as soon as each file lands, and it runs even when no new object exists. Glue ETL is correct for scheduled or event-triggered catalogue-based jobs. The stem demands immediate per-arrival triggering, which polling cannot satisfy.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.