Introduction to Cloud Computing

Service Models

1. Infrastructure as a Service (IaaS)
   • Definition: Provides raw compute, storage, and networking resources on demand.
   • User Responsibility: Operating system, middleware, runtime, applications, data.
   • Examples:
     • AWS EC2 + EBS + VPC
     • Azure Virtual Machines + Azure Storage + Virtual Network
     • GCP Compute Engine + Persistent Disk + VPC
2. Platform as a Service (PaaS)
   • Definition: Offers a managed platform—including OS, runtime, and middleware—so developers can deploy code without managing servers.
   • User Responsibility: Applications and data; the cloud provider handles the rest.
   • Examples:
     • AWS Elastic Beanstalk, AWS Fargate
     • Azure App Service, Azure Functions (serverless)
     • GCP App Engine, Cloud Run
3. Software as a Service (SaaS)
   • Definition: Delivers fully managed applications over the internet; end users simply consume the software without worrying about infrastructure or platforms.
   • User Responsibility: Data and user configuration only.
   • Examples:
     • Salesforce CRM, Google Workspace
     • AWS WorkMail, Azure DevOps Services
     • GCP G Suite, Firebase

Why Cloud Matters for DevOps

• Elasticity & Scalability
  • Auto-scale up/down in response to load—no need to over-provision.
• On-Demand Provisioning
  • Spin up environments in minutes via APIs or IaC.
• Pay-As-You-Go
  • Optimize costs by only paying for what you consume.
• Global Footprint
  • Deploy services close to users for low latency.
• Managed Services
  • Offload undifferentiated heavy lifting (databases, messaging, logging).

Deploying Applications in the Cloud

Key Cloud Service Categories

1. Compute
   • Virtual Machines: EC2, Compute Engine, Azure VMs
   • Containers & Orchestration: EKS/Elastic Kubernetes Service, AKS, GKE
   • Serverless: Lambda (AWS), Functions (Azure), Cloud Functions (GCP)
2. Storage & Databases
   • Object Storage: S3, Azure Blob Storage, Cloud Storage
   • Block Storage: EBS, Azure Disk Storage, Persistent Disk
   • Managed Databases: RDS/Aurora, Azure SQL Database, Cloud SQL / Spanner
3. Networking
   • Load Balancers: ELB/ALB, Azure Load Balancer/Application Gateway, Cloud Load Balancing
   • CDN: CloudFront, Azure CDN, Cloud CDN
   • DNS & Traffic Management: Route 53, Azure DNS, Cloud DNS
4. Identity & Access Management (IAM)
   • Centralized permission control: AWS IAM, Azure Active Directory, GCP IAM
   • Enables secure, least-privilege access for services and users.

Example Deployment Scenarios

• Microservice Application
  1. Build container images in CI (e.g., GitLab CI).
  2. Push to a registry (ECR, ACR, Artifact Registry).
  3. Deploy to Kubernetes (EKS/AKS/GKE) with Helm or GitOps.
  4. Configure auto-scaling via Horizontal Pod Autoscaler.