DEA-C01 Data Ingestion and Transformation Practice Question
A company uses AWS Glue to process data from Amazon RDS MySQL into Amazon S3. The Glue job uses a JDBC connection and runs on a schedule. Recently, the job has been failing with a 'Communications link failure' error. The RDS instance is in a private subnet. Which troubleshooting step should the data engineer take FIRST?
⚠ Common exam trap
Test-takers frequently assume 'Communications link failure' is a database-side issue (like connection limits or timeouts) and jump to tuning RDS parameters, when in fact it is most commonly a network connectivity problem in a VPC environment.
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
✓
Verify that the Glue job's VPC subnet and security group allow outbound traffic to RDS.
The 'Communications link failure' error typically indicates a network connectivity issue between the Glue job and the RDS instance. Since the RDS instance is in a private subnet, the Glue job must be configured with a VPC subnet and security group that allows outbound traffic to the RDS instance's security group on port 3306 (MySQL). Without this network path, the JDBC connection cannot be established, making verifying the VPC and security group configuration the first logical troubleshooting step.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Check the Glue job's DPU allocation; increase if too low.
Why it's wrong here
DPU limits cause performance issues, not connection errors.
- ✗
Review the Glue job script for data type mismatches.
Why it's wrong here
Data type mismatches cause parsing errors, not connection failures.
- ✓
Verify that the Glue job's VPC subnet and security group allow outbound traffic to RDS.
Why this is correct
Network connectivity is the first thing to check for link failures.
- ✗
Increase the RDS instance's max_connections parameter.
Why it's wrong here
Connection limit would cause 'too many connections' error, not link failure.
Visual reference
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
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.