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Cloud computing is the delivery of computing services — servers, storage, databases, networking, software, analytics, and intelligence — over the internet ("the cloud") to offer faster innovation, flexible resources, and economies of scale.
Before the cloud, organisations had to buy and maintain their own physical servers, storage devices, and networking equipment. This meant:
Cloud computing removes these constraints. You rent what you need, when you need it, and pay only for what you use.
The National Institute of Standards and Technology (NIST) defines five essential characteristics:
You can provision resources (servers, storage, etc.) automatically without needing human intervention from the provider.
Resources are available over the network and accessed through standard mechanisms — a web browser, CLI, or API.
The provider's resources are pooled to serve multiple customers using a multi-tenant model. You don't know (or need to know) the exact physical location of your resources.
Resources can be elastically provisioned and released to scale rapidly. To the consumer, the available resources often appear unlimited.
Cloud systems automatically control and optimise resource use by leveraging a metering capability. You only pay for what you consume.
There are three primary service models, each offering a different level of abstraction:
| Model | What You Manage | What the Provider Manages | Example |
|---|---|---|---|
| IaaS (Infrastructure as a Service) | OS, runtime, app, data | Servers, storage, networking | Amazon EC2, Azure VMs |
| PaaS (Platform as a Service) | App and data | OS, runtime, servers, storage | AWS Elastic Beanstalk, Heroku |
| SaaS (Software as a Service) | Nothing — just use it | Everything | Gmail, Salesforce, Slack |
You get virtual machines, storage, and networks. You install and manage the operating system and everything above it.
You deploy your application code. The provider handles the operating system, runtime, and infrastructure.
You use a finished application over the internet. The provider manages everything.
Resources are owned and operated by a third-party provider and delivered over the internet. Examples: AWS, Microsoft Azure, Google Cloud Platform (GCP).
Cloud infrastructure is provisioned for exclusive use by a single organisation. It can be on-premises or hosted by a third party.
A combination of public and private clouds, bound together by technology that allows data and applications to be shared between them.
| Benefit | Description |
|---|---|
| Trade capex for opex | No upfront hardware investment; pay as you go |
| Massive economies of scale | Providers buy at huge scale, passing savings to you |
| Stop guessing capacity | Scale up or down based on actual demand |
| Increase speed and agility | Provision resources in minutes, not months |
| Go global in minutes | Deploy to data centres worldwide with a few clicks |
| Focus on your product | Spend time on differentiation, not infrastructure |
Cloud computing fundamentally changes how organisations consume IT resources. Instead of owning hardware, you rent it on demand. Understanding the service models (IaaS, PaaS, SaaS) and deployment models (public, private, hybrid) is essential before diving into any specific cloud provider.
In the next lesson, we'll introduce Amazon Web Services (AWS) — the world's most widely adopted cloud platform.