Question 682 of 988
Fault Tolerance vs High Availability in AWS
A company runs a critical web application on a single Amazon EC2 instance in a single Availability Zone. The company wants to design the architecture so that the application continues to operate even if the physical server hosting the instance fails. Which AWS Cloud concept does this design objective primarily address?
Quick Answer
The answer is fault tolerance. This is correct because fault tolerance is the AWS cloud concept that ensures an application continues operating without interruption even when a physical server or underlying component fails, typically by deploying redundant resources across multiple Availability Zones. For the AWS Certified Cloud Practitioner CLF-C02 exam, this question tests your ability to distinguish fault tolerance from high availability: fault tolerance means zero downtime during a failure, while high availability minimizes downtime but may allow brief interruptions. A common trap is confusing the two, but remember that fault tolerance is about surviving failure with no impact, whereas high availability focuses on quick recovery. A helpful memory tip is to think of fault tolerance as a “no-break” guarantee—the system keeps running seamlessly—while high availability is a “fix-it-fast” promise.
⚠ Common exam trap
Many candidates confuse fault tolerance with high availability (HA), but the question specifically asks for the concept that ensures operation despite a physical server failure, which is fault tolerance, not just HA.
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
✓
Fault tolerance
Fault tolerance is the correct concept because the design objective is to ensure continuous operation despite the failure of a physical server hosting the EC2 instance. This is achieved by deploying the application across multiple Availability Zones (AZs) using an Auto Scaling group and an Elastic Load Balancer, so that if one instance or AZ fails, traffic is automatically routed to healthy instances in another AZ. The scenario explicitly focuses on surviving infrastructure failure, which is the core definition of fault tolerance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Elasticity
Why it's wrong here
Elasticity refers to automatically provisioning and de-provisioning resources to match demand. While important for handling variable traffic, it does not directly address continued operation during a physical server failure.
When this WOULD be correct
A company runs a web application on EC2 and expects traffic spikes. The design objective is to automatically add or remove instances to match demand. Elasticity would be the correct concept.
- ✗
Scalability
Why it's wrong here
Scalability is the ability to handle increasing workloads by adding resources. It focuses on growth and demand, not on maintaining operation when a specific component fails.
When this WOULD be correct
An exam question asking: 'A company expects a sudden spike in traffic to its web application. Which AWS Cloud concept should be used to automatically add EC2 instances to handle the load?' would make scalability the correct answer.
- ✓
Fault tolerance
Why this is correct
Fault tolerance is the correct concept. The objective is to remain operational despite a hardware failure. AWS supports this by allowing resources to be deployed across multiple isolated Availability Zones, so a failure in one zone does not affect instances in another.
- ✗
Cost optimization
Why it's wrong here
Cost optimization involves managing costs to maximize value. While fault-tolerant architectures may involve redundancy and additional cost, the primary objective described is about operational continuity, not cost reduction.
When this WOULD be correct
A company wants to reduce AWS spending by using Reserved Instances and right-sizing EC2 instances. The design objective is to minimize costs while meeting performance requirements.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CLF-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓Fault toleranceCorrect answer▾
Why this is correct
Fault tolerance is the correct concept. The objective is to remain operational despite a hardware failure. AWS supports this by allowing resources to be deployed across multiple isolated Availability Zones, so a failure in one zone does not affect instances in another.
✗ElasticityWrong answer — click to see why▾
Why this is wrong here
Elasticity refers to the ability to automatically scale resources up or down based on demand, not to ensure continued operation after a physical server failure. The question focuses on surviving a failure, not adjusting capacity.
★ When this WOULD be the correct answer
A company runs a web application on EC2 and expects traffic spikes. The design objective is to automatically add or remove instances to match demand. Elasticity would be the correct concept.
Why candidates choose this
Candidates may confuse elasticity with high availability or fault tolerance because both involve adding resources, but elasticity is about scaling to meet load, not surviving failures.
✗ScalabilityWrong answer — click to see why▾
Why this is wrong here
Scalability refers to the ability to handle increased load by adding resources, not to maintaining operation during a failure. The question specifically asks about continuing operation after a physical server failure, which is fault tolerance.
★ When this WOULD be the correct answer
An exam question asking: 'A company expects a sudden spike in traffic to its web application. Which AWS Cloud concept should be used to automatically add EC2 instances to handle the load?' would make scalability the correct answer.
Why candidates choose this
Candidates may confuse scalability with fault tolerance because both involve multiple instances, but scalability focuses on performance under load, not on surviving failures.
✗Cost optimizationWrong answer — click to see why▾
Why this is wrong here
Cost optimization focuses on minimizing expenses, not ensuring application continuity after a physical server failure. The question specifically asks about maintaining operation despite hardware failure, which is a fault tolerance concern.
★ When this WOULD be the correct answer
A company wants to reduce AWS spending by using Reserved Instances and right-sizing EC2 instances. The design objective is to minimize costs while meeting performance requirements.
Why candidates choose this
Candidates may confuse cost optimization with fault tolerance because implementing high availability often involves additional costs, leading them to think cost optimization is the primary goal when designing for resilience.
Analysis generated from the official CLF-C02blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Same concept, more angles
1 more way this is tested on CLF-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 customer-facing web application with an Amazon RDS database. Initially, the database is deployed as a single instance in one Availability Zone (AZ). A power outage occurs in that AZ, causing the database to become unavailable for several hours. After the incident, the company modifies the database to use a Multi-AZ configuration. Shortly after the change, another power outage affects the same primary AZ. This time, the database automatically fails over to the standby instance in the other AZ without any manual intervention, and the application remains available. Which cloud computing concept does this scenario best demonstrate?
medium- A.Elasticity
- ✓ B.Fault tolerance
- C.Scalability
- D.Resource pooling
Why B: Fault tolerance is the ability of a system to continue operating without interruption when one or more of its components fail. In this scenario, the Multi-AZ RDS deployment automatically failed over to a standby instance in a different Availability Zone when the primary AZ experienced a power outage, ensuring the application remained available without manual intervention. This demonstrates fault tolerance because the system was designed to withstand the failure of an entire AZ and continue functioning.
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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