CLF-C02 Cloud Technology and Services Practice Question
A company runs a web application on multiple Amazon EC2 instances that are behind an Application Load Balancer. The operations team wants to ensure that if any EC2 instance fails, a new instance is automatically launched to replace it and maintain a minimum number of running instances. Which AWS service should the company use to meet this requirement?
⚠ Common exam trap
Candidates often confuse Amazon EC2 Auto Scaling (which directly manages EC2 instance lifecycle and replacement) with AWS Auto Scaling (a broader service for scaling multiple resources), leading candidates to pick D instead of B.
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
✓
Amazon EC2 Auto Scaling
Amazon EC2 Auto Scaling is the correct service because it automatically launches new EC2 instances to replace failed ones and maintains a specified minimum number of running instances. It integrates with the Application Load Balancer to register new instances and deregister failed ones, ensuring the web application remains available. This directly meets the requirement for automatic instance replacement and capacity maintenance.
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 Elastic Load Balancing
Why it's wrong here
Elastic Load Balancing distributes incoming traffic across multiple targets, such as EC2 instances, but it does not automatically launch new instances to replace failed ones. It can perform health checks and route traffic away from unhealthy instances, but replacement is not its function.
When this WOULD be correct
A company needs to distribute incoming web traffic across multiple EC2 instances to improve fault tolerance and availability, with no requirement for automatic instance replacement.
- ✓
Amazon EC2 Auto Scaling
Why this is correct
Amazon EC2 Auto Scaling is the correct service. It automatically adds or removes EC2 instances based on defined policies or to maintain a desired capacity. If an instance fails, Auto Scaling detects the decrease in healthy capacity and launches a new instance to replace it, ensuring the application remains available.
- ✗
AWS Lambda
Why it's wrong here
AWS Lambda is a serverless compute service that executes code in response to events such as S3 object uploads, API Gateway requests, or SNS messages, abstracting away all underlying servers. It has no built-in capability to monitor EC2 instance health, maintain a desired instance count, or launch replacement instances, because it never manages EC2 infrastructure at all. Therefore, Lambda cannot replace failed EC2 instances and is fundamentally unrelated to the lifecycle management and automatic replenishment provided by Amazon EC2 Auto Scaling.
When this WOULD be correct
An exam scenario where the requirement is to automatically restart a stopped EC2 instance using a scheduled or event-driven function, such as using a Lambda function triggered by a CloudWatch alarm to start an instance that has stopped unexpectedly.
- ✗
AWS Auto Scaling
Why it's wrong here
AWS Auto Scaling is a service that helps you scale multiple AWS resources, including EC2 instances, DynamoDB tables, and Aurora replicas, using scaling plans. However, the specific service that directly manages EC2 instance replacement and desired capacity is Amazon EC2 Auto Scaling. AWS Auto Scaling provides a unified interface for scaling across resources, but for the described scenario, Amazon EC2 Auto Scaling is the appropriate service.
When this WOULD be correct
AWS Auto Scaling would be correct if the question asked about centrally managing scaling policies across multiple services, such as EC2 Auto Scaling, DynamoDB, and Aurora, or if the requirement was to create a scaling plan that coordinates scaling across different resources.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CLF-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓Amazon EC2 Auto ScalingCorrect answer▾
Why this is correct
Amazon EC2 Auto Scaling is the correct service. It automatically adds or removes EC2 instances based on defined policies or to maintain a desired capacity. If an instance fails, Auto Scaling detects the decrease in healthy capacity and launches a new instance to replace it, ensuring the application remains available.
✗AWS Elastic Load BalancingWrong answer — click to see why▾
Why this is wrong here
AWS Elastic Load Balancing distributes incoming traffic across targets but does not automatically replace failed instances or manage instance counts.
★ When this WOULD be the correct answer
A company needs to distribute incoming web traffic across multiple EC2 instances to improve fault tolerance and availability, with no requirement for automatic instance replacement.
Why candidates choose this
Candidates may confuse the high availability provided by load balancing with the automatic recovery and scaling capabilities of Auto Scaling.
✗AWS LambdaWrong answer — click to see why▾
Why this is wrong here
AWS Lambda is a serverless compute service that runs code in response to events, not a service for automatically replacing failed EC2 instances to maintain a minimum count.
★ When this WOULD be the correct answer
An exam scenario where the requirement is to automatically restart a stopped EC2 instance using a scheduled or event-driven function, such as using a Lambda function triggered by a CloudWatch alarm to start an instance that has stopped unexpectedly.
Why candidates choose this
Candidates may confuse Lambda's ability to respond to events (like instance failure) with the capability to manage instance lifecycle, not realizing that EC2 Auto Scaling is the dedicated service for maintaining instance counts.
✗AWS Auto ScalingWrong answer — click to see why▾
Why this is wrong here
AWS Auto Scaling is a service that helps you set up scaling policies for multiple AWS services, but it does not directly manage EC2 instance replacement or maintain a minimum number of running instances. The requirement to automatically launch a new instance when one fails is specifically handled by Amazon EC2 Auto Scaling, which manages the EC2 instances themselves.
★ When this WOULD be the correct answer
AWS Auto Scaling would be correct if the question asked about centrally managing scaling policies across multiple services, such as EC2 Auto Scaling, DynamoDB, and Aurora, or if the requirement was to create a scaling plan that coordinates scaling across different resources.
Why candidates choose this
Candidates may confuse AWS Auto Scaling with Amazon EC2 Auto Scaling due to the similar names, and assume that 'AWS Auto Scaling' is the service that handles EC2 instance scaling, when in fact it is a higher-level service for managing scaling across multiple AWS resources.
Analysis generated from the official CLF-C02blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CLF-C02 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 CLF-C02 exam.