← DOP-C02·Amazon Web Services

Question 1,411 of 1,740

Resilient Cloud Solutions →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is to enable EC2 instance recovery and configure ALB health checks to deregister unhealthy instances. This solution works because the ALB health check detects a failed instance, automatically deregisters it from the target group, and then EC2 instance recovery replaces the instance on the same underlying host, which triggers re-registration with the ALB. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how ALB health checks integrate with EC2 recovery actions to achieve automatic instance replacement without requiring Auto Scaling or manual intervention. A common trap is assuming Auto Scaling is needed, but instance recovery handles the replacement directly at the hypervisor level, while the ALB health check manages the traffic flow. Remember the key pairing: ALB health checks handle deregistration, and EC2 recovery handles replacement and re-registration—think of it as “check and replace” for seamless resilience.

DOP-C02 Resilient Cloud Solutions Practice Question

This DOP-C02 practice question tests your understanding of resilient cloud solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 web application on EC2 instances behind an ALB. To improve resilience, they want to automatically re-register failed instances. Which solution meets this requirement?

Question 1mediummultiple choice

Full question →

A
Set up a CloudWatch alarm to terminate the instance and notify an operator to re-register it.
Why wrong: CloudWatch alarms do not automatically re-register instances with ALB.
B
Enable EC2 instance recovery and configure ALB health checks to deregister unhealthy instances.
EC2 instance recovery replaces the instance and ALB health checks will automatically re-register it once healthy.
C
Configure Auto Scaling to launch a new instance on instance failure.
Why wrong: Auto Scaling can replace instances but does not automatically re-register them with the ALB without a health check integration.
D
Use Route 53 health checks to detect failure and update DNS to remove the instance.
Why wrong: Route 53 health checks affect DNS resolution, not ALB target group registration.

Full breakdown with real-world context →

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

✓

Enable EC2 instance recovery and configure ALB health checks to deregister unhealthy instances.

Option C is correct because an ALB health check failure triggers deregistration and, with instance recovery, the instance is replaced and re-registered. Option A is wrong because Auto Scaling launches new instances but doesn't automatically re-register failed ones without a scaling policy. Option B is wrong because Route 53 health checks don't manage instance registration with ALB. Option D is wrong because CloudWatch does not directly re-register instances.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Set up a CloudWatch alarm to terminate the instance and notify an operator to re-register it.
Why it's wrong here
CloudWatch alarms do not automatically re-register instances with ALB.
✓
Enable EC2 instance recovery and configure ALB health checks to deregister unhealthy instances.
Why this is correct
EC2 instance recovery replaces the instance and ALB health checks will automatically re-register it once healthy.
Related concept
Static NAT maps one inside address to one outside address.
✗
Configure Auto Scaling to launch a new instance on instance failure.
Why it's wrong here
Auto Scaling can replace instances but does not automatically re-register them with the ALB without a health check integration.
✗
Use Route 53 health checks to detect failure and update DNS to remove the instance.
Why it's wrong here
Route 53 health checks affect DNS resolution, not ALB target group registration.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

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. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. 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.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: Enable EC2 instance recovery and configure ALB health checks to deregister unhealthy instances. — Option C is correct because an ALB health check failure triggers deregistration and, with instance recovery, the instance is replaced and re-registered. Option A is wrong because Auto Scaling launches new instances but doesn't automatically re-register failed ones without a scaling policy. Option B is wrong because Route 53 health checks don't manage instance registration with ALB. Option D is wrong because CloudWatch does not directly re-register instances.

What should I do if I get this DOP-C02 question wrong?

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

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Same concept, more angles

1 more ways this is tested on DOP-C02

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A company runs a web application on EC2 instances behind an ALB. To improve resilience, they want to automatically replace failed instances and maintain a minimum number of instances. Which AWS service should be used?

easy

✓ A.Amazon EC2 Auto Scaling
B.AWS CloudFormation
C.AWS Elastic Beanstalk
D.AWS Systems Manager

Why A: Auto Scaling is designed to automatically replace failed instances and maintain a desired capacity, improving resilience.

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This DOP-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 DOP-C02 exam.