What Is Cloud Computing? AWS Services & the Cloud Model Explained

Before 2006, running a web application meant buying physical servers, renting space in a data centre, and waiting weeks for hardware to arrive. If you needed more capacity, you bought more hardware. If traffic dropped, those servers sat idle — costing money regardless.

Amazon Web Services changed the economics of computing permanently. This lesson explains what cloud computing is, how AWS is structured, and how to get your account ready for the rest of the course.

What Is Cloud Computing?

Cloud computing is the delivery of computing services — servers, storage, databases, networking, software, analytics — over the internet ("the cloud") on a pay-as-you-go basis.

Instead of owning infrastructure, you rent it. Instead of provisioning for peak load, you scale on demand. Instead of managing hardware, you consume services.

The five essential characteristics of cloud computing (per NIST):

1. On-demand self-service — provision resources without human interaction with the provider
2. Broad network access — accessible over the internet from any device
3. Resource pooling — provider's resources are shared across multiple customers (multi-tenancy)
4. Rapid elasticity — scale up or down quickly, often automatically
5. Measured service — usage is metered; you pay for what you consume

Cloud Deployment Models

Most modern applications run on public cloud, often AWS.

Cloud Service Models: IaaS, PaaS, SaaS

The cloud industry uses three service models to describe the level of abstraction provided:

Infrastructure as a Service (IaaS)

You manage: OS, runtime, application, data. Provider manages: virtualisation, servers, storage, networking.

Examples on AWS: EC2 (virtual machines), VPC (networking), EBS (block storage)

IaaS gives you the most control but requires the most management. It's the right choice when you need specific OS configurations, run legacy applications, or want full control over the environment.

Platform as a Service (PaaS)

You manage: application code and data. Provider manages: everything beneath your application.

Examples on AWS: Elastic Beanstalk, RDS (managed database), Lambda (serverless compute)

PaaS removes infrastructure management. You deploy code; the platform handles scaling, OS patches, and runtime.

Software as a Service (SaaS)

You manage: nothing. Provider manages: the entire stack including the application.

Examples: Gmail, Salesforce, GitHub. On AWS: WorkMail, Chime, QuickSight

The AWS Shared Responsibility Model

Security in the cloud is a shared responsibility between AWS and the customer. Understanding this boundary is critical — and heavily tested in the SAA-C03 exam.

AWS Responsibility ("Security OF the cloud"):
  ├── Physical facilities and hardware
  ├── Network infrastructure
  ├── Virtualisation layer
  └── Managed services patching (e.g., RDS OS patches)

Customer Responsibility ("Security IN the cloud"):
  ├── Operating system updates on EC2 instances
  ├── Application security and patching
  ├── Data encryption (in transit + at rest)
  ├── IAM configuration (who can access what)
  └── Network configuration (security groups, NACLs)

The line shifts depending on the service. For EC2 (IaaS), you own the OS. For RDS (PaaS), AWS owns the OS and database engine — you own the data and access controls.

Why AWS Dominates Cloud

AWS launched in 2006 — years before Azure (2010) or GCP (2011). That head start matters. Today AWS holds roughly 30–33% of the cloud market, consistently ahead of its competitors.

AWS by the Numbers

• 200+ services across compute, storage, database, AI/ML, networking, security, and more
• 33+ geographic regions globally (as of 2026)
• 105+ Availability Zones for redundancy within regions
• Used by over 1 million active customers including Netflix, Airbnb, NASA, and the UK NHS

AWS Core Service Categories

You don't need to know all 200+ services. The SAA-C03 exam focuses on ~40–50 core services. This course covers the most important ones.

Setting Up Your AWS Account

Step 1: Create a Root Account

Go to aws.amazon.com and create an account with your email address. This creates the root user — the most powerful identity in the account.

Important: After setup, stop using the root user for daily work. Create an IAM user or use IAM Identity Center instead. Lock the root user behind MFA and keep its credentials offline.

Step 2: Enable MFA on Root

1. Sign in as root
2. Click your account name → Security credentials
3. Under Multi-factor authentication (MFA) → Assign MFA device
4. Use an authenticator app (Google Authenticator, Authy)

Step 3: Set a Billing Alert

You never want a surprise AWS bill. Set a free-tier usage alert:

1. Open the Billing Dashboard (search "Billing" in the console)
2. Go to Billing preferences → Enable PDF invoices and free-tier alerts
3. Go to Budgets → Create a budget → Monthly cost budget → $10/month threshold

Step 4: Install the AWS CLI

# macOS (Homebrew)
brew install awscli

# Windows (winget)
winget install Amazon.AWSCLI

# Verify
aws --version

Configure with your credentials:

aws configure
# AWS Access Key ID: [your key]
# AWS Secret Access Key: [your secret]
# Default region name: us-east-1
# Default output format: json

Step 5: Explore the Console

The AWS Management Console (console.aws.amazon.com) is the web UI for all AWS services. Spend 10 minutes clicking around — explore the service search bar, the region selector (top right), and the billing dashboard.

Next: Lesson 2 — AWS Global Infrastructure

Part of the AWS Cloud Fundamentals course.

External references:

• AWS Free Tier — official overview of what's included in the 12-month free tier
• AWS Shared Responsibility Model — official documentation