Cloud computing changed how organisations build and run software. Instead of buying servers and running a data centre, you rent computing capacity from a provider like AWS on demand. This shift has made it faster and cheaper to launch new applications — and it's why cloud skills are in such high demand.
The NIST Definition
The widely used definition from the National Institute of Standards and Technology (NIST): Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort.
Simpler: you use computing power over the internet, pay for what you consume, and don't manage physical hardware.
The Six Advantages of Cloud Computing (AWS Framework)
- Trade capital expense for variable expense. Instead of buying hardware upfront (CapEx), you pay only for what you use (OpEx).
- Benefit from massive economies of scale. AWS serves millions of customers, so it achieves far lower costs per unit than any single organisation could alone.
- Stop guessing capacity. Scale up or down based on actual demand — no over-provisioning, no under-provisioning.
- Increase speed and agility. Launch new resources in minutes, not weeks. Experiment faster, fail cheaper.
- Stop spending money maintaining data centres. Focus on your application, not on racking servers and replacing failed hard drives.
- Go global in minutes. Deploy your application to multiple regions worldwide with a few clicks.
Cloud Service Models
IaaS — Infrastructure as a Service
The cloud provider manages physical infrastructure (servers, networking, storage). You manage the operating system, middleware, and applications.
Example: Amazon EC2 (virtual machines). You choose the instance type; AWS runs the physical hardware.
PaaS — Platform as a Service
The cloud provider manages the infrastructure and the operating system. You manage only your application and data.
Example: AWS Elastic Beanstalk, AWS App Runner. Deploy your app; AWS handles servers, OS patches, load balancing.
SaaS — Software as a Service
The provider manages everything — infrastructure, platform, and application. You just use the software.
Example: Amazon WorkMail, Salesforce, Gmail. No infrastructure management at all.
| Model | You manage | Provider manages |
|---|---|---|
| IaaS | OS, apps, data | Hardware, virtualisation, networking |
| PaaS | Apps, data | OS, runtime, hardware |
| SaaS | Data (usage) | Everything |
Cloud Deployment Models
- Public cloud: Resources are owned and operated by a third-party provider (AWS, Azure, GCP) and shared across customers. Most companies use public cloud for new workloads.
- Private cloud: Cloud infrastructure operated exclusively for one organisation, on-premises or hosted. Offers more control but higher cost.
- Hybrid cloud: A mix of public and private cloud, connected with data and applications portability between them. Common for regulated industries.
- Multi-cloud: Using services from multiple public cloud providers (e.g., AWS + Azure). Reduces vendor lock-in.
Key Cloud Concepts for the Exam
- Elasticity: Automatically scale resources up or down based on demand.
- Scalability: The ability to handle increased workload, either by scaling up (bigger instance) or scaling out (more instances).
- High Availability: Design systems to remain operational despite component failures, typically across multiple Availability Zones.
- Fault Tolerance: The system continues operating correctly even when one or more components fail.
- Agility: The speed at which cloud resources can be provisioned and decommissioned.
In the next lesson, you'll learn how AWS organises its global infrastructure into Regions, Availability Zones, and Edge Locations.