- A
AWS Systems Manager Automation with a custom runbook
Why wrong: AWS Systems Manager Automation can automate tasks, but it is less commonly used for direct RDS instance class modifications compared to Lambda. It is not the most direct method.
- B
AWS Auto Scaling with a target tracking scaling policy
Why wrong: AWS Auto Scaling with a target tracking scaling policy is designed for horizontal scaling (adding/removing read replicas). It does not support vertical scaling (changing the DB instance class) for RDS.
- C
AWS Lambda function to modify the DB instance class
An AWS Lambda function can be triggered by a CloudWatch alarm to call the RDS modify-db-instance API and change the instance class, enabling automated vertical scaling.
- D
Amazon CloudWatch Alarms to send an SNS notification to the DBA
Why wrong: CloudWatch Alarms can send SNS notifications, but they cannot directly modify the RDS instance. They require an action target (like Lambda) to perform the scaling.
DBS-C01 Vertical scaling Practice Question
This DBS-C01 practice question tests your understanding of management and operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: vertical scaling. 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.
A company's RDS for MySQL instance is experiencing high CPU utilization. Which AWS service should be used to set up automated actions to scale the instance vertically?
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
AWS Lambda function to modify the DB instance class
For automated vertical scaling of an RDS for MySQL instance, the most direct approach among the options is to use an AWS Lambda function that modifies the DB instance class, triggered by a CloudWatch alarm based on CPU utilization. AWS Auto Scaling (B) only supports horizontal scaling for RDS (adding read replicas) and does not natively change instance class. Systems Manager Automation (A) could orchestrate a change but is less straightforward than Lambda. CloudWatch Alarms (D) only notify; they cannot automatically scale without an action target like Lambda. Therefore, option C is the best choice.
Key principle: Vertical scaling
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AWS Systems Manager Automation with a custom runbook
Why it's wrong here
AWS Systems Manager Automation can automate tasks, but it is less commonly used for direct RDS instance class modifications compared to Lambda. It is not the most direct method.
- ✗
AWS Auto Scaling with a target tracking scaling policy
Why it's wrong here
AWS Auto Scaling with a target tracking scaling policy is designed for horizontal scaling (adding/removing read replicas). It does not support vertical scaling (changing the DB instance class) for RDS.
- ✓
AWS Lambda function to modify the DB instance class
Why this is correct
An AWS Lambda function can be triggered by a CloudWatch alarm to call the RDS modify-db-instance API and change the instance class, enabling automated vertical scaling.
Related concept
Vertical scaling
- ✗
Amazon CloudWatch Alarms to send an SNS notification to the DBA
Why it's wrong here
CloudWatch Alarms can send SNS notifications, but they cannot directly modify the RDS instance. They require an action target (like Lambda) to perform the scaling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates assume AWS Auto Scaling handles both horizontal and vertical scaling for RDS, but it only supports horizontal scaling (adding/removing replicas). Vertical scaling (changing instance class) requires a custom automation, such as a Lambda function triggered by CloudWatch Alarms.
Detailed technical explanation
How to think about this question
AWS Auto Scaling for RDS uses a target tracking policy that dynamically adjusts the DB instance class based on a predefined metric (e.g., CPU utilization) and a target value (e.g., 70%). Under the hood, it leverages CloudWatch metrics and the RDS ModifyDBInstance API to scale up or down, but note that vertical scaling typically incurs downtime during the modification, which is a key consideration for production workloads. In real-world scenarios, this is often combined with Multi-AZ deployments to minimize downtime during scaling events.
KKey Concepts to Remember
- Vertical scaling
- AWS Lambda
- CloudWatch Alarms
- AWS Auto Scaling
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
Vertical scaling
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.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
What to study next
Got this wrong? Here's your next step.
Review vertical scaling, then practise related DBS-C01 questions on the same topic to reinforce the concept.
- →
Management and Operations — study guide chapter
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Management and Operations practice questions
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Management and Operations — This question tests Management and Operations — Vertical scaling.
What is the correct answer to this question?
The correct answer is: AWS Lambda function to modify the DB instance class — For automated vertical scaling of an RDS for MySQL instance, the most direct approach among the options is to use an AWS Lambda function that modifies the DB instance class, triggered by a CloudWatch alarm based on CPU utilization. AWS Auto Scaling (B) only supports horizontal scaling for RDS (adding read replicas) and does not natively change instance class. Systems Manager Automation (A) could orchestrate a change but is less straightforward than Lambda. CloudWatch Alarms (D) only notify; they cannot automatically scale without an action target like Lambda. Therefore, option C is the best choice.
What should I do if I get this DBS-C01 question wrong?
Review vertical scaling, then practise related DBS-C01 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Vertical scaling
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Last reviewed: Jun 24, 2026
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