- A
Elasticity
Why wrong: 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.
- B
High availability
Why wrong: 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.
- C
Fault tolerance
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.
- D
Durability
Why wrong: 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.
Quick Answer
The answer is fault tolerance. This is the correct choice because fault tolerance describes a system designed to continue operating without any interruption, even when an entire AWS Availability Zone fails, by using duplicate, active infrastructure across multiple zones so that remaining components instantly take over with zero downtime. On the AWS Certified Cloud Practitioner CLF-C02 exam, this concept tests your ability to distinguish fault tolerance from high availability: high availability aims for minimal downtime (e.g., 99.99% uptime), while fault tolerance demands zero downtime and no data loss, making it the stricter requirement for mission-critical workloads like high-frequency trading. A common trap is choosing high availability when the scenario explicitly states “zero interruption” or “no downtime”—that is the hallmark of fault tolerance. Memory tip: think “fault tolerance = no tolerance for failure,” meaning the system survives a fault without any service impact.
CLF-C02 Cloud Concepts Practice Question
This CLF-C02 practice question tests your understanding of cloud concepts. 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 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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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.
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.
- ✗
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.
- ✗
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.
- ✓
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.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that 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.
Trap categories for this question
Scenario analysis trap
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.
Detailed technical explanation
How to think about this question
Fault tolerance in AWS is achieved by deploying identical, active-active workloads across multiple Availability Zones, often using services like Elastic Load Balancing with cross-zone load balancing and Auto Scaling groups configured for multiple AZs. Under the hood, the system must handle state replication (e.g., using Amazon ElastiCache for Redis with cluster mode or Amazon DynamoDB Global Tables) so that no session data is lost when an AZ fails. A real-world scenario is a high-frequency trading platform where even a single second of downtime could cause significant financial loss, so the architecture must be fully fault-tolerant, not just highly available.
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 Concepts — This question tests Cloud Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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