AZ-900 Describe cloud concepts Practice Question
A company hosts a critical line-of-business application on Azure virtual machines. The application must remain available even if a single virtual machine fails due to hardware failure or operating system crash. The company deploys two virtual machines in an Availability Set and configures an Azure Load Balancer to distribute traffic. If one VM becomes unavailable, the Load Balancer automatically redirects traffic to the healthy VM. This configuration primarily demonstrates which benefit of cloud computing?
⚠ Common exam trap
It's easy for candidates to confuse reliability (the ability to recover from failures and continue functioning) with elasticity (scaling), because both involve multiple VMs, but the key distinction is that reliability focuses on fault tolerance and automatic failover, not dynamic scaling based on load.
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
✓
Reliability – ability to recover from failures and continue functioning
This configuration demonstrates reliability, a core cloud computing benefit, because the combination of an Availability Set and Azure Load Balancer ensures that the application remains operational even when a single VM fails due to hardware or OS issues. The Availability Set spreads VMs across fault domains and update domains to isolate failures, while the Load Balancer uses health probes to detect VM unavailability and redirect traffic only to healthy instances. This built-in redundancy and automatic failover capability directly aligns with the cloud's promise of high availability and 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 – ability to scale resources up and down
Why it's wrong here
Elasticity refers to the ability to automatically scale computing resources (such as adding or removing VMs) in response to changing demand, often using Azure Virtual Machine Scale Sets or autoscaling rules. In contrast, the described architecture uses an Availability Set to place VMs across fault domains and a Load Balancer to distribute traffic, which is about resilience and recovery from a node failure, not about dynamically adjusting capacity. The goal is to sustain current availability, not to provision more resources when load increases.
When this WOULD be correct
A company runs an e-commerce application on Azure VMs that experiences variable traffic. They configure autoscaling to add VMs during peak hours and remove them during low traffic. This demonstrates elasticity.
- ✓
Reliability – ability to recover from failures and continue functioning
Why this is correct
Correct. The use of an Availability Set and Load Balancer ensures that the application can tolerate the failure of a single VM and continue serving traffic. This is a direct example of reliability, a key benefit of cloud computing.
- ✗
Security – protection against unauthorized access
Why it's wrong here
Security focuses on protecting workloads and data from unauthorized access, including identity management, encryption, network controls, and threat detection. The scenario mentions only an Availability Set and Load Balancer, which are high-availability and traffic distribution mechanisms, not security controls like network security groups, firewalls, or Azure Active Directory integration. Therefore, while security is a cloud benefit, it is not the benefit demonstrated by maintaining operation during a VM failure.
When this WOULD be correct
A question describing a company using Azure Firewall, network security groups, and encryption to protect virtual machines from external threats and data breaches would make security the correct answer.
- ✗
Cost efficiency – paying only for consumed resources
Why it's wrong here
Cost efficiency is about optimizing spend through the pay-as-you-go model and right-sizing resources, such as scaling down idle VMs or using reserved instances. In this scenario, the Availability Set and Load Balancer are redundant infrastructure components that ensure uptime during a failure, but they do not directly relate to reducing or optimizing cost. The design choice is specifically aimed at fault tolerance, not at minimizing Azure spend or improving cost management.
When this WOULD be correct
A question describing a company that deploys resources only during business hours and deallocates VMs overnight to reduce costs, asking which cloud benefit this demonstrates.
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 AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Reliability – ability to recover from failures and continue functioningCorrect answer▾
Why this is correct
Correct. The use of an Availability Set and Load Balancer ensures that the application can tolerate the failure of a single VM and continue serving traffic. This is a direct example of reliability, a key benefit of cloud computing.
✗Elasticity – ability to scale resources up and downWrong answer — click to see why▾
Why this is wrong here
The scenario describes fault tolerance and automatic recovery from VM failure, which is reliability, not elasticity. Elasticity refers to dynamically scaling resources up or down based on demand, which is not demonstrated here.
★ When this WOULD be the correct answer
A company runs an e-commerce application on Azure VMs that experiences variable traffic. They configure autoscaling to add VMs during peak hours and remove them during low traffic. This demonstrates elasticity.
Why candidates choose this
Candidates may confuse the ability to handle failures with scaling, or think that the Load Balancer's traffic distribution is a form of scaling, but it's about distributing load among existing VMs, not adjusting capacity.
✗Security – protection against unauthorized accessWrong answer — click to see why▾
Why this is wrong here
The scenario focuses on automatic recovery from VM failure via load balancing, which demonstrates reliability, not security. Security involves protecting data and systems from unauthorized access, which is not addressed here.
★ When this WOULD be the correct answer
A question describing a company using Azure Firewall, network security groups, and encryption to protect virtual machines from external threats and data breaches would make security the correct answer.
Why candidates choose this
Candidates may confuse high availability and fault tolerance with security, thinking that redundancy protects against attacks, or they may not distinguish between operational resilience and security controls.
✗Cost efficiency – paying only for consumed resourcesWrong answer — click to see why▾
Why this is wrong here
The scenario focuses on fault tolerance and automatic recovery from VM failure, not on cost optimization or pay-per-use billing.
★ When this WOULD be the correct answer
A question describing a company that deploys resources only during business hours and deallocates VMs overnight to reduce costs, asking which cloud benefit this demonstrates.
Why candidates choose this
Candidates may confuse the load balancer's traffic redirection as a cost-saving measure (avoiding idle resources) rather than recognizing it as a reliability feature.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
What is Cloud Computing?
Key term
Azure Load Balancer
Azure Load Balancer is a cloud service that evenly distributes incoming network traffic across multiple virtual machines or resources to ensure reliability and high availability.
Key term
High availability
High availability is a system design approach that aims to keep applications and services operational and accessible with minimal downtime, even when some components fail.
About these practice questions
This AZ-900 question is part of Courseiva's 981-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft 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 AZ-900 exam.