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Resilient Cloud Solutions →easyMultiple ChoiceObjective-mapped

Quick Answer

The answer is to configure the Auto Scaling group to launch instances across three Availability Zones with a desired capacity of 3. This is the most resilient configuration for single AZ failure because it ensures that even when one AZ goes down, the remaining two AZs still host at least two running instances, maintaining full service capacity while the Application Load Balancer automatically reroutes traffic away from the failed zone. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of how Auto Scaling group distribution and ALB health checks combine to achieve fault tolerance, with a common trap being to over-provision desired capacity or rely solely on a larger instance count in fewer AZs. The key insight is that resilience comes from spreading instances across all available AZs, not from sheer numbers alone. Memory tip: think “three AZs, three desired” — the magic number for surviving one failure is always n+1 AZs with at least one instance per AZ.

DOP-C02 Resilient Cloud Solutions Practice Question

This DOP-C02 practice question tests your understanding of resilient cloud 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 stateless web application on EC2 instances in an Auto Scaling group across three Availability Zones. The application uses an Application Load Balancer. The operations team needs to ensure that the application remains available if one AZ fails. Which solution is MOST resilient?

Question 1easymultiple choice
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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

✓

Configure the Auto Scaling group to launch instances in three Availability Zones with a desired capacity of 3.

Option C is correct because distributing instances across three Availability Zones (AZs) with a desired capacity of 3 ensures that even if one AZ fails, the remaining two AZs still have at least 2 instances running, maintaining service capacity. The Application Load Balancer (ALB) automatically routes traffic away from the failed AZ, and the Auto Scaling group will replace lost instances in the healthy AZs, providing the highest resilience against a single-AZ failure.

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.

  • ✗

    Configure the Auto Scaling group to launch instances in a single Availability Zone with a desired capacity of 6.

    Why it's wrong here

    A single AZ is a single point of failure.

  • ✗

    Configure the Auto Scaling group to launch instances in two Availability Zones with a desired capacity of 4.

    Why it's wrong here

    Two AZs provide redundancy but three AZs offer better resilience against a single AZ failure.

  • ✓

    Configure the Auto Scaling group to launch instances in three Availability Zones with a desired capacity of 3.

    Why this is correct

    Three AZs with at least one instance each ensures capacity remains in two AZs if one fails.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    Configure the Auto Scaling group to launch instances in two Availability Zones with a desired capacity of 6, all in one AZ.

    Why it's wrong here

    All instances in one AZ defeats the purpose of multi-AZ.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often think using two AZs is sufficient for high availability, but the question specifically asks for the 'MOST resilient' solution, and three AZs provide better fault isolation and recovery capacity than two, especially when the desired capacity is low.

Detailed technical explanation

How to think about this question

Under the hood, the ALB uses DNS-based routing and health checks to detect AZ failures; when an AZ becomes unhealthy, the ALB stops sending traffic to its targets, and the Auto Scaling group's rebalancing activity will launch new instances in the remaining healthy AZs to meet the desired capacity. In practice, distributing evenly across three AZs (e.g., 1 instance per AZ) ensures that a single AZ failure only reduces capacity by 33%, and the Auto Scaling group can quickly scale up in the healthy AZs, whereas with two AZs, a failure could reduce capacity by 50% or more, potentially causing performance degradation or throttling.

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

An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.

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.

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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 — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Configure the Auto Scaling group to launch instances in three Availability Zones with a desired capacity of 3. — Option C is correct because distributing instances across three Availability Zones (AZs) with a desired capacity of 3 ensures that even if one AZ fails, the remaining two AZs still have at least 2 instances running, maintaining service capacity. The Application Load Balancer (ALB) automatically routes traffic away from the failed AZ, and the Auto Scaling group will replace lost instances in the healthy AZs, providing the highest resilience against a single-AZ failure.

What should I do if I get this DOP-C02 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: Jun 11, 2026

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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.