- A
High availability
Why wrong: High availability refers to ensuring a system remains operational for a high percentage of time, often through redundancy and failover. However, it typically allows for a brief interruption during failover. The scenario states 'without any interruption', which aligns more closely with fault tolerance.
- B
Fault tolerance
Correct. Fault tolerance is the ability of a system to continue operating without interruption even when one or more components fail. The design where a failure of one VM causes no service disruption is a classic example of fault tolerance.
- C
Disaster recovery
Why wrong: Disaster recovery involves restoring systems and data after a major disaster (e.g., entire datacenter outage). The scenario describes a single VM failure within the same region, not a large-scale disaster.
- D
Scalability
Why wrong: Scalability is the ability to increase capacity to handle greater loads. This design focuses on resilience to failure, not on handling increased demand.
Quick Answer
The answer is fault tolerance. This design is correct because fault tolerance guarantees continuous operation without any interruption or loss of service, even when a component like a virtual machine fails due to hardware failure—it eliminates all single points of failure. In contrast, high availability reduces downtime but may allow brief interruptions during failover, such as when traffic reroutes to a standby instance. On the Microsoft Azure Fundamentals AZ-900 exam, this distinction tests your understanding of resilience characteristics; a common trap is confusing high availability with fault tolerance when the scenario explicitly states “no interruption.” Remember the memory tip: fault tolerance means “zero tolerance for downtime,” while high availability means “almost always up.”
AZ-900 Describe cloud concepts Practice Question
This AZ-900 practice question tests your understanding of describe cloud concepts. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: fault tolerance ensures zero downtime during component failure.. 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 critical transaction processing application on two Azure virtual machines. The infrastructure is designed so that if one virtual machine encounters a hardware failure and stops functioning, the other virtual machine continues to serve traffic without any interruption or loss of service. Which cloud computing characteristic does this design primarily address?
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
The design ensures that if one virtual machine fails due to a hardware failure, the other continues serving traffic without any interruption or loss of service. This is the definition of fault tolerance, which eliminates any single point of failure and maintains continuous operation even when a component fails. High availability reduces downtime but may allow brief interruptions during failover, whereas fault tolerance guarantees zero interruption.
Key principle: Fault tolerance ensures zero downtime during component failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
High availability
Why it's wrong here
High availability refers to ensuring a system remains operational for a high percentage of time, often through redundancy and failover. However, it typically allows for a brief interruption during failover. The scenario states 'without any interruption', which aligns more closely with fault tolerance.
- ✓
Fault tolerance
Why this is correct
Correct. Fault tolerance is the ability of a system to continue operating without interruption even when one or more components fail. The design where a failure of one VM causes no service disruption is a classic example of fault tolerance.
Related concept
Fault tolerance ensures zero downtime during component failure.
- ✗
Disaster recovery
Why it's wrong here
Disaster recovery involves restoring systems and data after a major disaster (e.g., entire datacenter outage). The scenario describes a single VM failure within the same region, not a large-scale disaster.
- ✗
Scalability
Why it's wrong here
Scalability is the ability to increase capacity to handle greater loads. This design focuses on resilience to failure, not on handling increased demand.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse high availability with fault tolerance, but high availability allows for brief downtime during failover, while fault tolerance guarantees zero interruption, which is the key distinction tested in this question.
Trap categories for this question
Scenario analysis trap
High availability refers to ensuring a system remains operational for a high percentage of time, often through redundancy and failover. However, it typically allows for a brief interruption during failover. The scenario states 'without any interruption', which aligns more closely with fault tolerance.
Detailed technical explanation
How to think about this question
Fault tolerance in Azure is achieved through technologies like Availability Zones, where VMs are placed in physically separate datacenters with independent power, cooling, and networking, and through load balancers that distribute traffic to healthy instances. Under the hood, Azure uses health probes (e.g., TCP or HTTP probes) to detect failures and instantly route traffic away from the failed VM, ensuring zero packet loss. In a real-world scenario, a financial transaction system using Azure Load Balancer with two VMs in different availability zones can survive a complete datacenter failure without any transaction being dropped.
KKey Concepts to Remember
- Fault tolerance ensures zero downtime during component failure.
- It often involves active-active redundancy or instant failover.
- Fault tolerance masks component failures from users/applications.
- Azure Availability Zones and Sets contribute to fault tolerance.
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
Fault tolerance ensures zero downtime during component failure.
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.
Review fault tolerance ensures zero downtime during component failure., then practise related AZ-900 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this AZ-900 question test?
Describe cloud concepts — This question tests Describe cloud concepts — Fault tolerance ensures zero downtime during component failure..
What is the correct answer to this question?
The correct answer is: Fault tolerance — The design ensures that if one virtual machine fails due to a hardware failure, the other continues serving traffic without any interruption or loss of service. This is the definition of fault tolerance, which eliminates any single point of failure and maintains continuous operation even when a component fails. High availability reduces downtime but may allow brief interruptions during failover, whereas fault tolerance guarantees zero interruption.
What should I do if I get this AZ-900 question wrong?
Review fault tolerance ensures zero downtime during component failure., then practise related AZ-900 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Fault tolerance ensures zero downtime during component failure.
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Last reviewed: Jun 11, 2026
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