Question 1,447 of 1,746
Continuous Improvement for Existing SolutionshardMultiple ChoiceObjective-mapped

Quick Answer

The answer is to change the Auto Scaling group health check type to ELB and integrate the custom health check with the ELB target group. This is correct because an Auto Scaling group configured with the default EC2 health check type only monitors instance status checks (system and reachability), ignoring any custom health metrics reported to CloudWatch. By switching to the ELB health check type, the Auto Scaling group uses the target group’s health status, which can reflect your custom health check logic if the instance is marked unhealthy by the load balancer. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding that Auto Scaling does not natively consume CloudWatch alarms for instance replacement—you must bridge the custom health check through an ELB target group or use EventBridge to trigger termination. A common trap is assuming CloudWatch alarms directly trigger replacement, but they require an intermediate service. Memory tip: “Custom health? Bridge it with ELB—don’t let CloudWatch alarms sit idle.”

SAP-C02 Continuous Improvement for Existing Solutions Practice Question

This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. 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 Amazon EC2 instances in an Auto Scaling group. The application uses a custom health check that reports instance health to Amazon CloudWatch. The Auto Scaling group is configured with an EC2 health check type. Recently, the company noticed that instances failing the custom health check are not being terminated and replaced. What should the solutions architect do to ensure that instances failing the custom health check are automatically replaced?

Question 1hardmultiple choice
Read the full NAT/PAT explanation →

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

Change the Auto Scaling group health check type to ELB and ensure the custom health check is integrated with the ELB target group.

Option D is correct because Auto Scaling only uses the EC2 status checks (system/reachability) by default. To use a custom health check, you must configure the Auto Scaling group to use ELB health checks and have the custom health check reported via a target group. Alternatively, you can use Amazon EventBridge to listen for custom health check failures and terminate instances. Option A is wrong because changing the health check type to ELB still requires a target group, and the custom health check must be integrated. Option B is wrong because CloudWatch alarms don't directly trigger instance replacement; you would need a lifecycle hook or EventBridge. Option C is wrong because manual termination defeats automation.

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.

  • Manually terminate the unhealthy instances from the EC2 console.

    Why it's wrong here

    Manual intervention defeats the purpose of automation.

  • Configure the Auto Scaling group to use instance metadata to report health.

    Why it's wrong here

    Instance metadata does not report health to Auto Scaling; Auto Scaling uses EC2 status checks or ELB health checks.

  • Create a CloudWatch alarm based on the custom health check metric and configure the alarm to terminate the instance.

    Why it's wrong here

    CloudWatch alarms do not have an action to terminate instances directly; you would need a lifecycle hook or Lambda.

  • Change the Auto Scaling group health check type to ELB and ensure the custom health check is integrated with the ELB target group.

    Why this is correct

    ELB health checks can be customized via the target group, and Auto Scaling will replace instances that fail ELB health checks.

    Related concept

    Static NAT maps one inside address to one outside address.

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 SAP-C02 NAT questions on configuration and troubleshooting.

Related practice questions

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FAQ

Questions learners often ask

What does this SAP-C02 question test?

Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: Change the Auto Scaling group health check type to ELB and ensure the custom health check is integrated with the ELB target group. — Option D is correct because Auto Scaling only uses the EC2 status checks (system/reachability) by default. To use a custom health check, you must configure the Auto Scaling group to use ELB health checks and have the custom health check reported via a target group. Alternatively, you can use Amazon EventBridge to listen for custom health check failures and terminate instances. Option A is wrong because changing the health check type to ELB still requires a target group, and the custom health check must be integrated. Option B is wrong because CloudWatch alarms don't directly trigger instance replacement; you would need a lifecycle hook or EventBridge. Option C is wrong because manual termination defeats automation.

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

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 SAP-C02 NAT questions on configuration and troubleshooting.

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

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Last reviewed: Jun 20, 2026

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