DEA-C01 Data Ingestion and Transformation Practice Question
A company runs a nightly ETL job using AWS Glue. The job reads data from a JDBC connection to an on-premises MySQL database. The job fails with an error indicating that the connection pool is exhausted. What is the most likely cause and solution?
⚠ Common exam trap
Watch out — candidates often confuse a database-side connection pool exhaustion with an AWS Glue service limit or network issue, leading them to incorrectly choose options about Glue connection pools or VPC configurations.
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
✓
The Glue job is using too many executors, exhausting the database connections. Reduce the number of DPUs or increase the database max connections.
AWS Glue jobs distribute work across multiple executors, each of which opens its own JDBC connection to the source database. When the number of executors (controlled by DPUs) exceeds the database's configured maximum connections, the database connection pool is exhausted, causing the error. Reducing the number of DPUs or increasing the database's max_connections setting resolves the issue.
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 database is not reachable due to network issues. Check VPC and security groups.
Why it's wrong here
Network issues cause timeouts, not pool exhaustion.
- ✗
The Glue job is hitting the AWS Glue connection pool limit. Increase the Glue connection pool size.
Why it's wrong here
AWS Glue has no user-adjustable connection pool limit; the exhaustion arises from the JDBC source's own connection limits or from too many concurrent Glue workers opening connections. Raising a nonexistent Glue pool size cannot help. It tempts because Glue connections do cap concurrent usage, so tuning them is valid for throughput, not for this error.
- ✗
The database credentials are expired. Rotate the password in AWS Secrets Manager.
Why it's wrong here
Expired credentials produce authentication failures, not pool exhaustion, so rotating the password leaves the connection leak unaddressed. It is tempting because Secrets Manager rotation genuinely resolves stale-credential errors, and would be correct if the job logged access-denied or token-expiry messages rather than pool saturation.
- ✓
The Glue job is using too many executors, exhausting the database connections. Reduce the number of DPUs or increase the database max connections.
Why this is correct
Each Glue executor opens its own JDBC connections, so a high DPU count multiplies concurrent sessions against the on-premises MySQL instance until its connection limit is hit. Reducing DPUs lowers that parallelism, directly addressing the exhausted connection pool constraint; raising MySQL's max_connections is the complementary fix.
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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.