AZ-900 Describe cloud concepts Practice Question
A company's CTO asks why Azure can offer services at lower costs than building an equivalent on-premises solution. Which cloud principle BEST explains this?
⚠ Common exam trap
Test-takers frequently confuse elasticity (scaling to meet demand) with cost savings, but elasticity reduces waste from over-provisioning, not the fundamental unit cost of compute or storage, which is where economies of scale provide the primary cost advantage.
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 is the correct answer because cloud providers like Azure operate massive, standardized data centers that serve millions of customers simultaneously. This allows them to negotiate bulk discounts on hardware, power, and cooling, and to spread fixed operational costs across a vast customer base, resulting in per-unit costs far lower than what a single company would pay for an equivalent on-premises deployment.
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 it's wrong here
Elasticity refers to the ability to dynamically add or remove resources, such as virtual machines or storage, in response to fluctuating demand. While this optimizes utilization and reduces waste, it does not lower the per-unit cost of infrastructure. Elasticity improves operational agility and cost control by matching capacity to actual usage, but it is unrelated to the procurement-scale discounts that cloud providers negotiate for hardware.
- ✓
Economies of scale
Why this is correct
Economies of scale is the correct concept: cloud providers aggregate the demand of millions of customers, enabling them to purchase compute, storage, and networking hardware in massive volumes. These bulk purchases secure significantly lower per-unit costs than smaller enterprises could obtain. Providers then pass a portion of these savings to customers through lower service prices, making cloud computing more affordable—a direct benefit of scale, not of dynamic scaling or geographic spread.
- ✗
High availability
Why it's wrong here
High availability ensures that applications remain operational during failures by using redundant components, automated failover, and load balancing across fault domains. This design principle focuses on maximizing uptime and minimizing downtime, often requiring additional resources and thus higher costs. High availability does not confer purchasing power or reduce the unit price of Azure services; it is a reliability characteristic that operates independently of scale-based pricing benefits.
- ✗
Geo-distribution
Why it's wrong here
Geo-distribution is the placement of cloud resources across multiple, globally dispersed Azure regions to reduce network latency, meet data residency requirements, and improve resilience. While this offers compliance and performance advantages, it does not inherently reduce the cost of infrastructure. In fact, maintaining resources in many regions can increase operational complexity and cost, so geo-distribution is not a driver of lower per-unit pricing.
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