DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
Add an additional standby instance in a third Availability Zone.
Why wrong: Multi-AZ already has a standby; additional standbys are not supported.
B
Increase the connection pool timeout in the application configuration.
Why wrong: This would only delay the timeout, not resolve the underlying connection issue.
C
Create a read replica and direct write traffic to it.
Why wrong: Read replicas are for read traffic, not writes.
D
Increase the DB instance class to handle more concurrent connections.
A larger instance can handle more connections and reduce timeouts.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often 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.
Detailed technical explanation
How to think about this question
In Amazon RDS for MySQL, the `max_connections` parameter is automatically derived from the DB instance's memory allocation using the formula `DBInstanceClassMemory / 12582880`. For example, a db.r5.large instance (16 GiB RAM) defaults to around 1,360 connections, while a db.r5.xlarge (32 GiB RAM) defaults to about 2,720 connections. When the application exhausts this limit, new connections receive an 'Too many connections' error, which is exactly the symptom shown. Scaling the instance class increases both memory and the connection ceiling without requiring application code changes.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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