DBS-C01 Workload-Specific Database Design Practice Question
Exhibit
Refer to the exhibit. Error log from application connecting to Amazon RDS for MySQL: "ERROR 1040 (08004): Too many connections" Current RDS configuration: db.r5.large, max_connections = 1000 (default).
An application is receiving the error shown in the exhibit. The application uses connection pooling. The RDS instance is a db.r5.large with max_connections set to 1000. What is the most likely cause?
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 connection pool in the application is not releasing idle connections.
If the application's connection pool does not release idle connections, it can exhaust the maximum connections even though max_connections is set appropriately. Option A is incorrect because if the security group blocked connections, the application would receive a timeout or 'connection refused' error, not an error indicating max connections are reached. Option B is incorrect because max_connections is set to 1000, which is the default for a db.r5.large instance and is typically sufficient; the instance size supports that value. Option D is incorrect because a different VPC would cause network connectivity issues (e.g., timeout) rather than a 'too many connections' error, which indicates the connection is established but the limit is reached.
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 security group is blocking incoming connections.
Why it's wrong here
If the security group blocked connections, the application would receive a timeout or 'connection refused' error, not an error indicating max connections are reached.
- ✗
The max_connections parameter is set too low for the instance size.
Why it's wrong here
The max_connections parameter is set to 1000, which is the default for a db.r5.large instance and is typically sufficient; the instance size supports that value.
- ✓
The connection pool in the application is not releasing idle connections.
Why this is correct
If the application's connection pool does not release idle connections, it can exhaust the maximum connections even though max_connections is set appropriately.
- ✗
The RDS instance is in a different VPC than the application.
Why it's wrong here
A different VPC would cause network connectivity issues (e.g., timeout) rather than a 'too many connections' error, which indicates the connection is established but the limit is reached.
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Same concept, more angles
1 more way this is tested on DBS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company's application is logging the error shown in the exhibit. The application is deployed on Amazon EC2 and connects to an Amazon RDS for MySQL Multi-AZ DB instance. Which configuration change is most likely to resolve this issue?
easy- A.Add an additional standby instance in a third Availability Zone.
- B.Increase the connection pool timeout in the application configuration.
- C.Create a read replica and direct write traffic to it.
- ✓ D.Increase the DB instance class to handle more concurrent connections.
Why D: The error log indicates that the application is hitting the maximum number of connections allowed by the RDS DB instance. Increasing the DB instance class (Option D) provides more memory and CPU resources, which allows the instance to support a higher `max_connections` value (calculated as `DBInstanceClassMemory / 12582880` for MySQL). This directly resolves the connection limit issue without changing the application's connection pool behavior or architecture.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-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 DBS-C01 exam.