CLF-C02 Cloud Concepts Practice Question
A financial services company runs a high-frequency stock trading platform on AWS. The platform must continue processing trades without any interruption, even if an entire AWS Availability Zone experiences a complete outage. The architecture is designed with duplicate infrastructure in multiple Availability Zones, and all components are active simultaneously. The system is engineered so that if one AZ fails, the remaining AZs continue processing trades instantly, with zero downtime for end users. Which cloud computing concept does this requirement BEST represent?
⚠ Common exam trap
Watch out — candidates often confuse high availability with fault tolerance, but high availability allows for a brief failover period (e.g., seconds of downtime), while fault tolerance requires zero downtime and instant continuity, which is the exact requirement in this question.
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
This requirement describes a system that continues to operate without any interruption even when an entire AWS Availability Zone fails. That is the definition of fault tolerance: the system is designed to survive component failures with zero impact on service. The architecture uses duplicate active infrastructure in multiple AZs so that if one AZ fails, the remaining AZs instantly take over with no downtime, which is fault tolerance, not just high availability.
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 the ability to automatically scale computing resources up or down based on demand. While the platform may also be elastic, the core requirement described is about surviving a failure with zero interruption, not about scaling.
When this WOULD be correct
A question describing a workload with variable traffic (e.g., e-commerce site during Black Friday) that must automatically add or remove EC2 instances to match demand would make elasticity the correct answer.
- ✗
High availability
Why it's wrong here
High availability typically involves redundant components and automatic failover, but it generally allows for a short period of downtime (seconds or minutes) during the failover process. The scenario explicitly states 'zero downtime,' which is a more stringent requirement that aligns with fault tolerance.
When this WOULD be correct
A question that asks for a design ensuring minimal downtime (e.g., 99.99% uptime) with automatic failover but allows for a brief interruption (e.g., a few seconds) during a failure. For example: 'An e-commerce website must remain accessible during an AZ outage with automatic recovery within 30 seconds.'
- ✓
Fault tolerance
Why this is correct
Fault tolerance is the property that enables a system to continue functioning correctly even when some of its components fail. The scenario's demand for 'zero downtime' and 'instant' continuation of processing after an AZ failure directly matches the definition of fault tolerance. This is typically achieved through active-active redundant deployments.
- ✗
Durability
Why it's wrong here
Durability refers to the long-term protection of data from loss or corruption, often associated with storage services like Amazon S3 (e.g., 99.999999999% durability). It is not related to application uptime or continued processing during an infrastructure failure.
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 property that enables a system to continue functioning correctly even when some of its components fail. The scenario's demand for 'zero downtime' and 'instant' continuation of processing after an AZ failure directly matches the definition of fault tolerance. This is typically achieved through active-active redundant deployments.
✗ElasticityWrong answer — click to see why▾
Why this is wrong here
Elasticity refers to the ability to scale resources up or down based on demand, not to survive an AZ outage with zero downtime. The requirement is about continuous operation despite failures, not dynamic scaling.
★ When this WOULD be the correct answer
A question describing a workload with variable traffic (e.g., e-commerce site during Black Friday) that must automatically add or remove EC2 instances to match demand would make elasticity the correct answer.
Why candidates choose this
Candidates may confuse the ability to handle failures with the ability to handle load changes, or think that scaling across AZs is the same as fault tolerance.
✗High availabilityWrong answer — click to see why▾
Why this is wrong here
High availability focuses on minimizing downtime through redundant components and failover, but it typically involves some recovery time (e.g., seconds to minutes). The requirement for zero downtime and instant failover with no interruption is the defining characteristic of fault tolerance, not high availability.
★ When this WOULD be the correct answer
A question that asks for a design ensuring minimal downtime (e.g., 99.99% uptime) with automatic failover but allows for a brief interruption (e.g., a few seconds) during a failure. For example: 'An e-commerce website must remain accessible during an AZ outage with automatic recovery within 30 seconds.'
Why candidates choose this
Candidates often confuse high availability with fault tolerance because both involve redundancy and failover. The term 'high availability' is more commonly used, leading them to select it without recognizing the stricter zero-downtime requirement of fault tolerance.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.