- A
AWS Lambda
Why wrong: Lambda could be used with custom automation, but it is not the native service for this purpose.
- B
EC2 Instance Connect
Why wrong: EC2 Instance Connect allows SSH access but does not manage instance health or replacement.
- C
Auto Scaling group
Auto Scaling groups can use ELB health checks to automatically replace unhealthy instances.
- D
Amazon CloudWatch
Why wrong: CloudWatch can monitor and alarm but cannot automatically terminate and replace instances.
Question 478 of 1,705
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. 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.
A company runs a critical application on EC2 instances behind an Application Load Balancer. They need to ensure that if an instance fails health checks, it is automatically terminated and replaced. Which AWS service should they use?
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
✓
Auto Scaling group
An Auto Scaling group (Option C) is the correct service because it automatically replaces unhealthy EC2 instances by integrating with the Application Load Balancer's health checks. When an instance fails the configured health check (e.g., HTTP 5xx or TCP timeout), the Auto Scaling group marks it as unhealthy, terminates it, and launches a new instance to maintain the desired capacity. This lifecycle management is a core feature of Auto Scaling groups, not available in the other options.
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.
- ✗
AWS Lambda
Why it's wrong here
Lambda could be used with custom automation, but it is not the native service for this purpose.
- ✗
EC2 Instance Connect
Why it's wrong here
EC2 Instance Connect allows SSH access but does not manage instance health or replacement.
- ✓
Auto Scaling group
Why this is correct
Auto Scaling groups can use ELB health checks to automatically replace unhealthy instances.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon CloudWatch
Why it's wrong here
CloudWatch can monitor and alarm but cannot automatically terminate and replace instances.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates might choose Amazon CloudWatch (Option D) because they know CloudWatch can monitor health checks and trigger actions, but they overlook that CloudWatch alone cannot directly terminate and replace EC2 instances—it requires additional automation (e.g., Lambda or Auto Scaling), making Auto Scaling the correct and complete answer for automatic replacement.
Detailed technical explanation
How to think about this question
Under the hood, an Auto Scaling group uses the ELB health check mechanism (e.g., HTTP/HTTPS health checks on a specific path) to determine instance health. When an instance fails the health check, the Auto Scaling group waits for the 'health check grace period' (default 300 seconds) before initiating termination, preventing flapping. In a real-world scenario, if the application's health check endpoint returns a 503 due to a memory leak, the Auto Scaling group will terminate the instance and launch a new one, but if the root cause is an AMI issue, all new instances will also fail, requiring a lifecycle hook or CloudWatch alarm to pause scaling.
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
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Auto Scaling group — An Auto Scaling group (Option C) is the correct service because it automatically replaces unhealthy EC2 instances by integrating with the Application Load Balancer's health checks. When an instance fails the configured health check (e.g., HTTP 5xx or TCP timeout), the Auto Scaling group marks it as unhealthy, terminates it, and launches a new instance to maintain the desired capacity. This lifecycle management is a core feature of Auto Scaling groups, not available in the other options.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This ANS-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 ANS-C01 exam.
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