Amazon Web Services (AWS) is the largest public cloud. This note covers the foundations: global infrastructure, the responsibility split, pricing, and design principles. See also The Big Three and Cloud Computing Services.

Services at a glance

Service	Purpose
AWS Organizations	Multi-account management, consolidated billing, SCPs
AWS Control Tower	Set up a governed multi-account landing zone
AWS Cost Explorer / Budgets	Analyse and cap spend
AWS Pricing Calculator	Estimate costs
AWS Trusted Advisor	Checks for cost, performance, security, fault tolerance, limits
AWS Well-Architected Tool	Review workloads against the framework
AWS Health Dashboard	Service health and events affecting you
AWS CloudTrail	API call audit log
AWS Config	Resource configuration history and compliance
AWS Artifact	Compliance reports and agreements
AWS Support	Basic, Developer, Business, Enterprise On-Ramp, Enterprise

Hands-on companion: sharifndlovu123/aws-playground, a lab of about 60 AWS services explored through the CLI, IaC and SDKs.

Why Cloud (Benefits)

Trade upfront (CapEx) for variable (OpEx) expense
Economies of scale lead to lower per-unit prices
Stop guessing capacity: scale up and down on demand
Speed and agility: resources in minutes
Stop spending on running datacentres
Go global in minutes

Global Infrastructure

Term	Meaning
Region	A geographic area with multiple isolated Availability Zones (e.g. `af-south-1` Cape Town, `eu-west-1` Ireland)
Availability Zone (AZ)	One or more discrete datacentres with redundant power, networking and connectivity; each region has 3+
Edge locations	Points of presence for CloudFront and Route 53 that cache and route near users
Regional edge caches	Larger caches between origin and edge
Local Zones	Extend a region closer to a city for single-digit ms latency
Wavelength	Compute at 5G network edges
Outposts	AWS hardware in your datacentre

Choosing a region: compliance / data residency, latency to users, service availability, price.

Services are regional (EC2, VPC, S3 buckets live in a region), global (IAM, Route 53, CloudFront) or AZ-scoped (a subnet, an EC2 instance).

Shared Responsibility Model

AWS: security of the cloud: hardware, facilities, global network, managed service software
Customer: security in the cloud: data, IAM, OS patching (EC2), security groups, encryption choices, client-side config

Example	Responsible
Patching the hypervisor	AWS
Patching the guest OS on EC2	You
Patching the OS under RDS	AWS
S3 bucket policy and public access	You
Physical datacentre access	AWS
IAM users and MFA	You

Responsibility shifts toward AWS as you move EC2 → RDS → Lambda → SaaS.

Pricing Principles

Pay as you go: on-demand per second / hour / GB
Save when you commit: Savings Plans, Reserved Instances (1 or 3 year)
Pay less as you use more: tiered pricing, volume discounts
Free tier: always-free, 12-month free, and short trials
Data transfer: inbound free, outbound to the internet charged, transfer between AZs/regions charged

EC2 purchase options

Option	Best for
On-Demand	Short, unpredictable workloads
Savings Plans	Steady usage, flexible across instance families
Reserved Instances	Steady, specific instance config
Spot	Fault-tolerant, flexible jobs, up to ~90% off, can be reclaimed with 2 min warning
Dedicated Hosts / Instances	Licence rules, compliance
Capacity Reservations	Guarantee capacity in an AZ

Cost tools

Cost Explorer: visualise and forecast
Budgets: alerts on actual or forecast spend
Cost and Usage Report (CUR): most detailed data
Cost allocation tags, Consolidated Billing (Organizations) for volume discounts

AWS Well-Architected Framework: Six Pillars

Operational Excellence: run and monitor, improve continuously
Security: protect data and systems, least privilege
Reliability: recover from failure, scale to meet demand
Performance Efficiency: use resources efficiently
Cost Optimization: avoid unneeded cost
Sustainability: minimise environmental impact

AWS Cloud Adoption Framework (CAF)

Perspectives: Business, People, Governance, Platform, Security, Operations. Guides organisations through cloud transformation.

Migration: the 7 Rs

Retire, Retain, Rehost (lift-and-shift), Relocate, Repurchase, Replatform, Refactor. Tools: Application Migration Service, Database Migration Service (DMS), Migration Hub, Snow Family (Snowcone, Snowball, Snowmobile) for offline transfer.

Ways to Interact with AWS

Management Console: web GUI
AWS CLI: aws commands
SDKs: Python (Boto3), JavaScript, Java, .NET, Go...
CloudShell: browser shell with CLI pre-installed
Infrastructure as Code: CloudFormation, CDK

$ aws configure
$ aws sts get-caller-identity
$ aws ec2 describe-regions --output table