DEA-C01 Redshift JDBC connection Practice Question
A company runs a nightly AWS Glue ETL job that writes results to an Amazon Redshift table using the JDBC connector. Recently, the job has been failing with the error 'ERROR: connection to server at ... failed: server closed the connection unexpectedly'. The Redshift cluster is in a private subnet with a VPC endpoint for S3. The Glue job runs in the same VPC with enhanced VPC routing enabled. Which is the most likely cause?
⚠ Common exam trap
Candidates may assume that SSL is optional, but many production Redshift clusters enforce SSL, causing non-SSL connections to be dropped.
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
✓
SSL is not enabled on the Redshift cluster.
The error 'server closed the connection unexpectedly' typically indicates that the Redshift cluster rejected the connection, often because SSL is required but not enabled in the Glue JDBC connection. Redshift clusters can be configured with the `require_ssl` parameter set to true, forcing all connections to use SSL. Option B is correct because without SSL, the server terminates the connection. Option A is incorrect because the 'redshift' compatibility mode is not a standard requirement; the JDBC driver works without it. Option C is incorrect because security group issues would cause a timeout or 'connection refused', not a server-side close. Option D is incorrect because Glue supports Redshift as a data source.
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 JDBC driver is missing the 'redshift' compatibility mode setting.
Why it's wrong here
The 'redshift' compatibility mode is not a standard requirement for Glue-JDBC connections; the error is not caused by missing this setting.
- ✓
SSL is not enabled on the Redshift cluster.
Why this is correct
Correct. If the Redshift cluster enforces SSL, the connection will be rejected without SSL, causing the 'server closed the connection unexpectedly' error.
- ✗
The Glue job's security group does not allow outbound traffic to the Redshift cluster.
Why it's wrong here
Security group misconfiguration leads to timeout or 'connection refused', not a server-side close of an established connection.
- ✗
AWS Glue does not support Redshift as a data source.
Why it's wrong here
AWS Glue natively supports Redshift as a data source via JDBC.
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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JA
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.