DBS-C01 Workload-Specific Database Design Practice Question
Exhibit
Refer to the exhibit. Amazon CloudWatch log snippet: 2023-03-15T10:00:00.000Z [WARN] Connection to database 'customers' timed out. Retrying... 2023-03-15T10:00:05.000Z [ERROR] Maximum retries exceeded. Unable to establish connection to RDS instance 'customers-cluster-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?
⚠ Common exam trap
Many exam-takers confuse connection pool timeout adjustments (Option B) with connection limit increases, but timeout only affects how long a request waits, not the hard limit imposed by the database engine's `max_connections` parameter.
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
✓
Increase the DB instance class to handle more concurrent connections.
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add an additional standby instance in a third Availability Zone.
Why it's wrong here
Multi-AZ already has a standby; additional standbys are not supported.
- ✗
Increase the connection pool timeout in the application configuration.
Why it's wrong here
This would only delay the timeout, not resolve the underlying connection issue.
- ✗
Create a read replica and direct write traffic to it.
Why it's wrong here
Read replicas are for read traffic, not writes.
- ✓
Increase the DB instance class to handle more concurrent connections.
Why this is correct
A larger instance can handle more connections and reduce timeouts.
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