What is Cloud Computing?
Cloud computing delivers computing services—servers, storage, databases, networking, software—over the internet ("the cloud"). Instead of owning physical data centres, you rent access from a cloud provider and pay only for what you use.
Key Benefits
- Trade fixed expense for variable expense — pay only for what you consume.
- Benefit from massive economies of scale — providers aggregate usage from hundreds of thousands of customers.
- Stop guessing capacity — scale up or down within minutes.
- Increase speed and agility — new resources available in seconds.
- Go global in minutes — deploy in multiple regions around the world.
Cloud Deployment Models
- Public Cloud — Resources owned and operated by a third-party provider, delivered over the internet (e.g., AWS, Azure, GCP).
- Private Cloud — Cloud resources used exclusively by a single organisation, hosted on-premises or by a third party.
- Hybrid Cloud — Combines public and private clouds, allowing data and applications to be shared between them.
AWS Global Infrastructure
AWS operates a global infrastructure spanning Regions, Availability Zones (AZs), and Edge Locations.
Regions
A Region is a physical location in the world containing multiple, isolated data centres called Availability Zones. Each Region is completely independent. When selecting a Region consider: data governance/legal requirements, proximity to customers, service availability, and pricing.
Availability Zones
An AZ is one or more discrete data centres with redundant power, networking, and connectivity within a Region. AZs are physically separated—typically tens of miles apart—to protect against disasters, while remaining close enough for low-latency replication. Deploying across multiple AZs gives high availability.
Edge Locations
AWS CloudFront edge locations cache content closer to end users to reduce latency. There are many more edge locations than Regions. AWS Local Zones extend AWS infrastructure to more geographic locations for applications that require single-digit millisecond latency.
Cloud Service Models
Infrastructure as a Service (IaaS)
Provides virtualised computing resources over the internet. You manage: OS, middleware, runtime, data, applications. Provider manages: virtualisation, servers, storage, networking. Example: Amazon EC2.
Platform as a Service (PaaS)
Provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the underlying infrastructure. Example: AWS Elastic Beanstalk, AWS Lambda.
Software as a Service (SaaS)
Delivers software applications over the internet, on demand and typically on a subscription basis. Provider manages everything. Example: Amazon WorkMail, Salesforce.
Shared Responsibility Model
AWS is responsible for security of the cloud (physical hardware, global infrastructure, managed services). You are responsible for security in the cloud (data, IAM, OS patches, network/firewall configuration, client-side encryption).