AZ-900 Describe cloud concepts Practice Question
A small business runs its IT infrastructure in a small on-premises server room. The business owner is considering moving to Azure and asks the IT manager: 'How can a large cloud provider like Microsoft offer compute and storage at a lower per-unit cost than I can get by purchasing my own servers, even though I only need a few virtual machines?' Which cloud computing benefit best answers this question?
⚠ Common exam trap
Test-takers frequently confuse economies of scale with elasticity, thinking that scaling resources up/down automatically reduces per-unit cost, when in fact elasticity only optimizes total cost by matching usage, not the underlying unit price of compute or storage.
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
✓
Economies of scale
Economies of scale allow Microsoft to spread massive capital and operational costs (data center construction, power, cooling, hardware procurement) across millions of customers. This per-unit cost reduction means even a small business consuming only a few virtual machines benefits from the same low-cost infrastructure that a large enterprise would, making Azure's compute and storage cheaper than purchasing and maintaining dedicated on-premises servers.
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 an architectural property that ensures applications remain operational during component or infrastructure failures, typically by deploying redundant virtual machines, load balancers, and failover clusters across multiple availability zones. These measures increase the total hardware and operational footprint, which raises rather than lowers the per-unit cost of running a workload. The question asks why a small business pays less per unit in the cloud than on-premises, and high availability does not address the provider's underlying cost advantage from scale.
When this WOULD be correct
A question asking: 'Which cloud benefit ensures that a virtual machine remains accessible even if the underlying physical server fails?' would make high availability the correct answer.
- ✗
Elasticity
Why it's wrong here
Elasticity is the ability to provision and release resources automatically in response to fluctuating demand, which helps a customer avoid paying for idle capacity and reduces overall waste. However, elasticity is a consumer-side usage pattern that affects how much capacity you purchase, not the unit price of that capacity. The lower per-unit cost in cloud computing stems from the provider's economies of scale—negotiating cheaper hardware, energy, and bandwidth—not from the ability to scale resources up and down, which would apply even if per-unit costs were identical to on-premises.
When this WOULD be correct
A question asking: 'Which cloud benefit allows a company to automatically add virtual machines during peak traffic and remove them when traffic decreases?' would make elasticity the correct answer.
- ✓
Economies of scale
Why this is correct
Economies of scale occur when a provider's large size enables it to purchase hardware, energy, and bandwidth at much lower prices per unit. These savings are passed to customers, making cloud services cost-effective even for small deployments.
- ✗
Fault tolerance
Why it's wrong here
Fault tolerance goes beyond high availability by allowing a system to continue operating without any noticeable interruption, which requires fully duplicated components and real-time data replication. Building fault tolerance is deliberately expensive because every critical component must have an identical standby, and that overhead is directly opposite to the cost savings from bulk purchasing. While cloud providers offer fault-tolerant services, this design characteristic is unrelated to the economic principle that makes their base infrastructure costs lower than an on-premises data center.
When this WOULD be correct
An exam question asking: 'Which cloud benefit ensures that a critical application remains operational even if a hardware component fails in the data center?' would make fault tolerance the correct answer.
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.
✓Economies of scaleCorrect answer▾
Why this is correct
Economies of scale occur when a provider's large size enables it to purchase hardware, energy, and bandwidth at much lower prices per unit. These savings are passed to customers, making cloud services cost-effective even for small deployments.
✗High availabilityWrong answer — click to see why▾
Why this is wrong here
High availability refers to ensuring systems remain operational despite failures, not to cost reduction from large-scale operations. The question asks about lower per-unit cost, which is explained by economies of scale, not high availability.
★ When this WOULD be the correct answer
A question asking: 'Which cloud benefit ensures that a virtual machine remains accessible even if the underlying physical server fails?' would make high availability the correct answer.
Why candidates choose this
Candidates may confuse high availability with the general reliability and cost benefits of cloud, or think that high availability implies efficient resource use that lowers costs.
✗ElasticityWrong answer — click to see why▾
Why this is wrong here
Elasticity refers to the ability to scale resources up or down based on demand, which does not explain the lower per-unit cost achieved by a large cloud provider compared to a small business purchasing its own servers.
★ When this WOULD be the correct answer
A question asking: 'Which cloud benefit allows a company to automatically add virtual machines during peak traffic and remove them when traffic decreases?' would make elasticity the correct answer.
Why candidates choose this
Candidates may confuse elasticity with cost savings, thinking that scaling resources automatically reduces costs, but the question specifically asks about lower per-unit cost due to provider size, not dynamic scaling.
✗Fault toleranceWrong answer — click to see why▾
Why this is wrong here
Fault tolerance refers to a system's ability to continue operating despite component failures, which does not explain why a large cloud provider can offer lower per-unit costs compared to a small business purchasing its own servers.
★ When this WOULD be the correct answer
An exam question asking: 'Which cloud benefit ensures that a critical application remains operational even if a hardware component fails in the data center?' would make fault tolerance the correct answer.
Why candidates choose this
Candidates may confuse fault tolerance with cost benefits, thinking that built-in redundancy reduces overall expenses, but fault tolerance is about reliability, not cost efficiency.
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
Economies of scale
Economies of scale is the cost advantage that businesses get when production becomes more efficient as they grow larger, reducing the cost per unit.
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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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.