The answer is to deregister the unhealthy instances from the target group. This immediately stops the Application Load Balancer from routing any new traffic to them, as deregistration forces the ALB to complete in-flight requests and remove the instance from its routing table, bypassing any misconfigured health checks or lingering draining states. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of how ALB target group registration works versus health check status—a common trap is assuming a failed health check alone stops traffic, but an instance remains registered and can still receive connections if the health check logic is flawed. Remember the memory tip: "Deregister, don't just diagnose"—health checks detect, but deregistration disconnects. This distinction is critical for high-availability SAP deployments where rapid traffic isolation is needed during failed rollouts.
PAS-C01 Operations and Maintenance Practice Question
This PAS-C01 practice question tests your understanding of operations and maintenance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is running a critical web application on EC2 instances behind an Application Load Balancer. During a recent deployment, a new version of the application was released, and within minutes, the error rate spiked. The operations team rolled back the deployment, but the error rate remained high. The team suspects that the ALB is still routing traffic to unhealthy instances. Which step should the team take to immediately stop routing traffic to the problematic instances?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deregister the instances from the target group.
Option D is correct because deregistering the problematic EC2 instances from the target group immediately stops the Application Load Balancer from routing any new traffic to them. The ALB performs health checks on registered targets, but if an instance is unhealthy, it still remains in the target group and can receive traffic if the health check logic is misconfigured or if the instance is in a 'draining' state. Deregistration forces the ALB to complete any in-flight requests and then remove the instance from the routing table, providing an immediate stop to traffic.
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.
✗
Modify the ALB listener rules to point to a different target group.
Why it's wrong here
This does not immediately stop traffic to the unhealthy instances in the original target group.
✗
Modify the health check interval to 5 seconds and the unhealthy threshold to 2.
Why it's wrong here
This only speeds up detection of unhealthy instances but does not immediately stop traffic.
✗
Stop the EC2 instances from the AWS Management Console.
Why it's wrong here
Stopping instances takes time and may cause issues if they are still receiving traffic.
✓
Deregister the instances from the target group.
Why this is correct
Deregistering immediately stops routing traffic to those instances.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'health check failure' with 'immediate traffic removal,' not realizing that health checks only update the instance's status but do not stop traffic until the instance is explicitly deregistered or the health check threshold is met, which introduces a delay.
Detailed technical explanation
How to think about this question
Under the hood, the ALB uses a connection table and target group registration to route traffic. When an instance is deregistered, the ALB immediately stops sending new connections to it and initiates connection draining (default 300 seconds) to allow existing requests to complete. This is governed by the AWS Elastic Load Balancing API, which updates the routing table in near real-time, typically within seconds. In contrast, health check failures only mark an instance as unhealthy but do not remove it from the target group; the instance remains in the 'unhealthy' state and can still receive traffic if the health check is not properly configured or if the ALB's health check logic is overridden by sticky sessions.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Operations and Maintenance — This question tests Operations and Maintenance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deregister the instances from the target group. — Option D is correct because deregistering the problematic EC2 instances from the target group immediately stops the Application Load Balancer from routing any new traffic to them. The ALB performs health checks on registered targets, but if an instance is unhealthy, it still remains in the target group and can receive traffic if the health check logic is misconfigured or if the instance is in a 'draining' state. Deregistration forces the ALB to complete any in-flight requests and then remove the instance from the routing table, providing an immediate stop to traffic.
What should I do if I get this PAS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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