What is Cloud Computing?
Cloud computing is like renting a computer instead of buying one. Let's break down what that really means — and why every organisation is moving to the cloud.
What is cloud computing, really?
Think of it like electricity.
A hundred years ago, factories had to generate their own electricity. They built generators, hired engineers to maintain them, and worried about power failures.
Then the power grid was invented. Now you just plug into the wall and pay for what you use. You don’t need to know how the power plant works — you just need the electricity.
Cloud computing is the same idea, but for computing. Instead of buying servers, you rent them. Instead of maintaining hardware, someone else does it. You just use what you need and pay for what you use.
Before the cloud: the old way
Picture this: you work at a company that needs a new application. In the traditional (on-premises) world, here’s what happens:
- You estimate how many users will use the app
- You buy servers — physical machines that sit in a room
- You wait weeks or months for delivery
- You set them up — install the operating system, configure networking, secure them
- You maintain them — patch updates, replace failed hardware, pay for electricity and cooling
- You hope your estimate was right. Too few servers? The app crashes. Too many? You’ve wasted money on hardware sitting idle.
This is expensive, slow, and risky. And it’s exactly what cloud computing fixes.
The cloud way
With cloud computing:
- You decide what you need — a virtual machine, a database, storage
- You provision it in minutes (not months)
- You scale up or down based on actual demand
- You pay only for what you use
- Microsoft maintains the physical hardware, cooling, power, and security
Real-world example: Black Friday
Imagine you run an online store. On a normal day, you need 2 servers. On Black Friday, you need 50.
On-premises: You’d need to buy and maintain 50 servers year-round, even though you only need them for one day.
In the cloud: You spin up 48 extra servers on Black Friday morning, and shut them down that night. You only pay for the hours you used them.
This is called elasticity — one of the key benefits of cloud computing.
Key advantages of cloud computing
Here are the benefits Microsoft wants you to know for the exam:
| Advantage | What It Means |
|---|---|
| High availability | Your apps stay running even when things fail |
| Scalability | Add more resources as demand grows |
| Elasticity | Scale up AND down automatically |
| Agility | Deploy new resources in minutes, not months |
| Geo-distribution | Deploy close to your users worldwide |
| Disaster recovery | Backups and failover protect your data |
What's the difference between scalability and elasticity?
They sound similar but there’s a key difference:
- Scalability means you can grow — the system supports adding more resources
- Elasticity means the system automatically grows and shrinks based on demand
Think of a rubber band: it’s elastic because it stretches when pulled and snaps back when released. A cloud that’s elastic automatically adds servers during a traffic spike and removes them when traffic drops — without you lifting a finger.
Meet the characters
Throughout this course, you’ll follow four organisations as they adopt Azure:
| Character | Who They Are | Azure Use Cases |
|---|---|---|
| 🏪 Peak Roasters | Small coffee roastery, 15 staff, moving to the cloud for the first time | Website hosting, email, simple storage, budget-conscious decisions |
| 🏥 Harbour Health | Mid-size healthcare company, 500 staff, hybrid cloud for compliance | Identity, security, networking, governance, regulated data |
| 🎓 Kai | University IT student, learning Azure via the free tier | Hands-on portal work, serverless, student projects, beginner perspective |
| 🏗️ Summit Construction | Growing construction firm, 200 staff, migrating from on-premises | VMs, migration, IaC, cost optimisation, scaling for project surges |
These scenarios help anchor abstract concepts to real situations — exactly how the exam tests you.
The shared responsibility model
This is a big one for the exam. When you move to the cloud, security responsibilities are shared between you and the cloud provider.
The core idea: Microsoft manages the physical infrastructure (servers, cooling, networking, buildings). You manage your data, identities, and access controls. The exact split depends on whether you use IaaS, PaaS, or SaaS — we’ll cover the detailed breakdown in Module 6.
| What Microsoft Manages | What You Manage |
|---|---|
| Physical datacenter security | Your data and information |
| Power, cooling, networking | Your identities and access controls |
| Physical hosts and servers | Devices that connect to the cloud |
Key takeaway: No matter what cloud model you use, you are always responsible for your data and your identities. Microsoft will never take responsibility for what you store or who you give access to.
🎬 Video walkthrough
🎬 Video coming soon
What is Cloud Computing? — AZ-900 Domain 1
What is Cloud Computing? — AZ-900 Domain 1
~8 minFlashcards
Test yourself on the key concepts from this module:
Knowledge Check
Which of the following is a benefit of cloud computing that allows resources to automatically increase or decrease based on demand?
In the shared responsibility model, who is responsible for physical security of the data centre when using Azure?
Which cloud computing advantages help ensure that applications remain available during hardware failures? (Select TWO)
Next up: We’ll look at the different types of cloud models — public, private, and hybrid — and when to use each one.