AZ-900 Describe cloud concepts Practice Question
A company runs an e-commerce web application on Azure virtual machines that are part of a virtual machine scale set configured with an autoscale rule based on CPU utilization. During a flash sale, customer traffic surges, causing the average CPU utilization across all instances to exceed 75% for five minutes. The scale set automatically provisions three additional VM instances to handle the increased load. After the sale ends, traffic normalizes, CPU utilization drops below 30%, and the scale set automatically removes the extra instances. This scenario best illustrates which characteristic of cloud computing?
⚠ Common exam trap
Test-takers frequently confuse elasticity (dynamic scaling to meet demand) with high availability (redundancy for uptime), as both involve multiple VMs but serve fundamentally different purposes.
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
✓
Elasticity
Elasticity is the ability of a cloud system to dynamically scale resources up or down based on demand. In this scenario, the virtual machine scale set automatically adds three VM instances when CPU utilization exceeds 75% for five minutes and removes them when utilization drops below 30%, demonstrating rapid, automated scaling to match workload changes.
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 this is correct
Correct. Elasticity is the cloud characteristic that enables automatic provisioning and de-provisioning of resources to match workload demand. The autoscale behavior described—adding instances during high CPU usage and removing them when usage drops—is a textbook example of elasticity.
- ✗
High availability
Why it's wrong here
Incorrect. High availability refers to designing systems to remain operational with minimal downtime, often through redundancy and failover. While a scale set can contribute to availability, the scenario specifically describes scaling up/down based on demand rather than maintaining uptime during failures.
When this WOULD be correct
A question describing a web application deployed across multiple Azure availability zones with a load balancer that automatically redirects traffic if a zone fails, ensuring the app remains online. The correct answer would be high availability because it emphasizes continuous operation during failures.
- ✗
Fault tolerance
Why it's wrong here
Incorrect. Fault tolerance is the ability of a system to continue operating correctly even when one or more of its components fail. The scenario does not describe any failures; it describes adapting to changes in load.
When this WOULD be correct
A question describing an application that automatically reroutes traffic to healthy instances when a VM fails, ensuring continuous operation without downtime, would make fault tolerance the correct answer.
- ✗
Disaster recovery
Why it's wrong here
Incorrect. Disaster recovery involves policies and processes for restoring IT infrastructure and data after a catastrophic event such as a natural disaster or large-scale outage. The scenario is about handling normal traffic fluctuations, not recovering from a disaster.
When this WOULD be correct
A company's primary Azure region experiences a prolonged outage due to a natural disaster. The company has a disaster recovery plan that automatically fails over the e-commerce application to a secondary Azure region using Azure Site Recovery, ensuring business continuity.
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.
✓ElasticityCorrect answer▾
Why this is correct
Correct. Elasticity is the cloud characteristic that enables automatic provisioning and de-provisioning of resources to match workload demand. The autoscale behavior described—adding instances during high CPU usage and removing them when usage drops—is a textbook example of elasticity.
✗High availabilityWrong answer — click to see why▾
Why this is wrong here
High availability focuses on ensuring the application remains accessible despite component failures, not on automatically scaling resources up and down based on demand. The scenario describes dynamic resource adjustment, not fault tolerance or uptime guarantees.
★ When this WOULD be the correct answer
A question describing a web application deployed across multiple Azure availability zones with a load balancer that automatically redirects traffic if a zone fails, ensuring the app remains online. The correct answer would be high availability because it emphasizes continuous operation during failures.
Why candidates choose this
Candidates may confuse elasticity (scaling resources) with high availability because both involve multiple instances and automatic responses, but high availability is about redundancy and failover, not scaling based on load.
✗Fault toleranceWrong answer — click to see why▾
Why this is wrong here
Fault tolerance refers to a system's ability to continue operating without interruption despite component failures, not to dynamic scaling of resources based on demand. The scenario describes adding/removing VMs based on load, not handling failures.
★ When this WOULD be the correct answer
A question describing an application that automatically reroutes traffic to healthy instances when a VM fails, ensuring continuous operation without downtime, would make fault tolerance the correct answer.
Why candidates choose this
Candidates may confuse fault tolerance with elasticity because both involve automatic responses to changing conditions, but fault tolerance focuses on failure recovery, not scaling.
✗Disaster recoveryWrong answer — click to see why▾
Why this is wrong here
Disaster recovery involves restoring IT infrastructure and data after a catastrophic event (e.g., natural disaster, cyberattack) using backups and alternate sites. This scenario describes automatic scaling of VMs based on demand, not recovery from a disaster.
★ When this WOULD be the correct answer
A company's primary Azure region experiences a prolonged outage due to a natural disaster. The company has a disaster recovery plan that automatically fails over the e-commerce application to a secondary Azure region using Azure Site Recovery, ensuring business continuity.
Why candidates choose this
Candidates may confuse the automatic provisioning of resources during a traffic surge with recovery from a failure, mistakenly thinking that scaling out to handle load is a form of disaster recovery.
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
Cloud computing
Cloud computing is the on-demand delivery of IT resources over the internet, allowing users to access computing power, storage, and applications without owning physical hardware.
Key term
Elasticity
Elasticity is the ability of a cloud system to automatically add or remove computing resources (like servers, storage, or bandwidth) in response to real-time changes in demand.
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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.