- A
Multiple EC2 instances in a single Availability Zone
Why wrong: Multiple instances in a single AZ protects against individual instance failures but not against an AZ-wide outage — all instances fail simultaneously.
- B
EC2 instances distributed across at least two Availability Zones behind an ALB
Deploying instances across multiple AZs with an ALB spanning those AZs ensures that an outage in one AZ doesn't take down the application — traffic automatically routes to the surviving AZ.
- C
A single large EC2 instance with enhanced networking
Why wrong: A single instance, regardless of size, is a single point of failure — any instance or AZ failure takes down the application.
- D
EC2 instances in a single Region across multiple subnets in the same AZ
Why wrong: Multiple subnets within the same AZ don't provide AZ fault tolerance — they all fail if the AZ goes down.
Quick Answer
The answer is EC2 instances distributed across at least two Availability Zones behind an Application Load Balancer. This is the minimum architecture for AZ outage resilience because the ALB can only route traffic to healthy targets, and if all instances reside in a single AZ that fails, the load balancer has no healthy targets to serve. By deploying instances in two separate AZs and configuring the ALB with subnets in those same AZs, the application remains available even if one entire AZ goes down. On the AWS Certified Cloud Practitioner CLF-C02 exam, this scenario tests your understanding of high availability versus fault tolerance at the AZ level—a common trap is thinking the ALB alone provides resilience, but it requires multi-AZ targets to function. Remember the memory tip: “Two AZs, one ALB—survive an AZ calamity.”
CLF-C02 Cloud Technology and Services Practice Question
This CLF-C02 practice question tests your understanding of cloud technology and services. 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 is running their application on EC2 instances behind an Application Load Balancer. They want to ensure the application remains available during an AZ outage. What is the minimum architecture configuration required?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
EC2 instances distributed across at least two Availability Zones behind an ALB
To remain available during an Availability Zone outage, the application must be resilient to the failure of an entire AZ. An Application Load Balancer distributes traffic across healthy targets, but it cannot route to instances in a failed AZ. Therefore, EC2 instances must be deployed in at least two separate Availability Zones, and the ALB must be configured with subnets in those same AZs to route traffic and perform health checks, ensuring continuous availability if one AZ goes down.
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.
- ✗
Multiple EC2 instances in a single Availability Zone
Why it's wrong here
Multiple instances in a single AZ protects against individual instance failures but not against an AZ-wide outage — all instances fail simultaneously.
- ✓
EC2 instances distributed across at least two Availability Zones behind an ALB
Why this is correct
Deploying instances across multiple AZs with an ALB spanning those AZs ensures that an outage in one AZ doesn't take down the application — traffic automatically routes to the surviving AZ.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A single large EC2 instance with enhanced networking
Why it's wrong here
A single instance, regardless of size, is a single point of failure — any instance or AZ failure takes down the application.
- ✗
EC2 instances in a single Region across multiple subnets in the same AZ
Why it's wrong here
Multiple subnets within the same AZ don't provide AZ fault tolerance — they all fail if the AZ goes down.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'multiple subnets' with 'multiple Availability Zones,' assuming that deploying across subnets within the same AZ provides fault tolerance, but subnets are AZ-scoped and do not offer AZ-level redundancy.
Detailed technical explanation
How to think about this question
Under the hood, an Application Load Balancer operates at the target group level, where you register EC2 instances across multiple AZs. The ALB uses cross-zone load balancing by default, distributing traffic evenly across healthy instances in all enabled AZs. During an AZ outage, the ALB’s health checks (HTTP/HTTPS health checks on configured paths) will mark instances in the failed AZ as unhealthy, and traffic is automatically rerouted to healthy instances in the remaining AZs, provided at least one healthy target remains.
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 CLF-C02 question test?
Cloud Technology and Services — This question tests Cloud Technology and Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: EC2 instances distributed across at least two Availability Zones behind an ALB — To remain available during an Availability Zone outage, the application must be resilient to the failure of an entire AZ. An Application Load Balancer distributes traffic across healthy targets, but it cannot route to instances in a failed AZ. Therefore, EC2 instances must be deployed in at least two separate Availability Zones, and the ALB must be configured with subnets in those same AZs to route traffic and perform health checks, ensuring continuous availability if one AZ goes down.
What should I do if I get this CLF-C02 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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
This CLF-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 CLF-C02 exam.
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