AZ-900 Describe cloud concepts Practice Question
A retail company runs an e-commerce website on Azure. The website experiences highly unpredictable traffic with occasional sudden spikes (e.g., during flash sales). Outside of sales events, the website has low traffic. The company wants to automatically increase the number of virtual machines during peak demand and automatically reduce them when demand subsides, without any manual intervention. The primary goal is to handle variable demand efficiently while minimizing cost. Which cloud computing characteristic best describes this capability?
⚠ Common exam trap
Candidates often confuse 'scalability' (the ability to handle growth) with 'elasticity' (the ability to automatically and dynamically adjust resources in real time), but the question's emphasis on automatic, demand-driven scaling and cost minimization points specifically to elasticity.
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 correct answer because it specifically refers to the ability of a cloud system to automatically provision and de-provision resources (such as virtual machines) in response to real-time demand changes. In this scenario, the e-commerce website needs to scale out during flash sales and scale in during low traffic periods without manual intervention, which is the defining characteristic of elasticity. This capability directly supports the goal of handling variable demand efficiently while minimizing cost, as resources are only consumed when needed.
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 is a measure of a system's operational uptime, aiming to minimize downtime through redundancy, failover mechanisms, and rapid recovery from failures. It ensures that the e-commerce site remains reachable and responsive even during component outages, but it does not imply automatic scaling of resources in real time based on traffic patterns. The scenario's focus on adjusting VM count to match variable demand is elasticity, not the availability-focused guarantees that high availability provides.
When this WOULD be correct
A company requires its e-commerce website to remain accessible with minimal downtime during a regional Azure outage. The primary goal is to ensure continuous operation despite failures, using multiple availability zones or regions.
- ✗
Fault tolerance
Why it's wrong here
Fault tolerance refers to a system's ability to continue operating without interruption when one or more components fail, typically by duplicating components and automatically failing over to redundant ones. The scenario describes a website whose VM count changes with traffic volume, not a response to hardware or software failures. While fault tolerance might involve adding VMs during a failure, it does not explain proactive, demand-driven scaling to handle fluctuating load.
When this WOULD be correct
A question asking: 'An e-commerce site must remain operational even if an Azure region fails. Which characteristic ensures this?' — Fault tolerance would be correct as it describes the ability to continue functioning despite failures.
- ✗
Scalability
Why it's wrong here
Incorrect but plausible. Scalability is the capacity to handle increased load by adding resources. However, scalability does not inherently imply automatic scaling up and down. It can be manual or planned. Elasticity is the more precise term for automatic, dynamic scaling based on demand.
When this WOULD be correct
A company expects steady growth in user traffic over the next year and wants to ensure its application can handle the increased load by adding more virtual machines. The primary goal is to support growth, not to handle fluctuating demand. In this case, scalability is the correct characteristic.
- ✓
Elasticity
Why this is correct
Correct. Elasticity is the cloud characteristic that allows resources to be automatically provisioned and de-provisioned in real time to match current demand. The automatic addition and removal of VMs in response to variable traffic directly demonstrates elasticity, which helps manage costs by only paying for what is used.
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 allows resources to be automatically provisioned and de-provisioned in real time to match current demand. The automatic addition and removal of VMs in response to variable traffic directly demonstrates elasticity, which helps manage costs by only paying for what is used.
✗High availabilityWrong answer — click to see why▾
Why this is wrong here
High availability ensures the system remains operational during failures, but does not automatically adjust resources based on demand spikes. The question focuses on scaling resources up/down with traffic, not uptime.
★ When this WOULD be the correct answer
A company requires its e-commerce website to remain accessible with minimal downtime during a regional Azure outage. The primary goal is to ensure continuous operation despite failures, using multiple availability zones or regions.
Why candidates choose this
Candidates may confuse high availability with the ability to handle variable demand, as both involve maintaining performance under changing conditions, but high availability is about redundancy and uptime, not dynamic scaling.
✗Fault toleranceWrong answer — click to see why▾
Why this is wrong here
Fault tolerance ensures system operation during component failures, not automatic scaling based on demand. The question focuses on handling variable traffic by adding/removing VMs, which is elasticity, not fault tolerance.
★ When this WOULD be the correct answer
A question asking: 'An e-commerce site must remain operational even if an Azure region fails. Which characteristic ensures this?' — Fault tolerance would be correct as it describes the ability to continue functioning despite failures.
Why candidates choose this
Candidates may confuse fault tolerance with scalability or elasticity, thinking that handling spikes requires tolerance of increased load, but fault tolerance specifically addresses failures, not demand changes.
✗ScalabilityWrong answer — click to see why▾
Why this is wrong here
Scalability refers to the ability to handle increased load by adding resources, but it does not inherently include automatic reduction of resources when demand subsides. Elasticity specifically includes automatic scaling both up and down, which is required for the described scenario of handling unpredictable spikes and minimizing cost.
★ When this WOULD be the correct answer
A company expects steady growth in user traffic over the next year and wants to ensure its application can handle the increased load by adding more virtual machines. The primary goal is to support growth, not to handle fluctuating demand. In this case, scalability is the correct characteristic.
Why candidates choose this
Candidates often confuse scalability with elasticity because both involve adjusting resources to meet demand. They may think scalability includes automatic scaling in both directions, but in cloud computing, scalability typically refers to the ability to scale up (or out) to meet increased demand, while elasticity adds the automatic scaling down capability.
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
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.
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.
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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.