Service Models: IaaS, PaaS, SaaS
Cloud services are typically organized into three layers. Each layer determines what the provider manages and what you manage. Understanding this division is fundamental to using the cloud effectively.
The Responsibility Spectrum
┌──────────────────────────────────────────────────────────┐
│ YOU MANAGE │
│ ┌────────────────────────────────────────────────────┐ │
│ │ SaaS │ │
│ │ Just use the app (Gmail, Salesforce, Slack) │ │
│ │ Provider handles: Everything else │ │
│ ├────────────────────────────────────────────────────┤ │
│ │ PaaS │ │
│ │ You manage: App code + data │ │
│ │ Provider handles: OS, runtime, servers, network │ │
│ ├────────────────────────────────────────────────────┤ │
│ │ IaaS │ │
│ │ You manage: OS, apps, data, middleware │ │
│ │ Provider handles: Virtualization, servers, storage│ │
│ ├────────────────────────────────────────────────────┤ │
│ │ On-Premises │ │
│ │ You manage: Everything │ │
│ └────────────────────────────────────────────────────┘ │
│ PROVIDER MANAGES │
└──────────────────────────────────────────────────────────┘
IaaS — Infrastructure as a Service
The cloud provider gives you virtual machines, storage, and networking. You install and manage everything else. It's like renting a bare building — you bring the furniture, utilities, and staff.
Examples: AWS EC2, Azure Virtual Machines, Google Compute Engine
Best for: System administrators who want full control without buying hardware.
PaaS — Platform as a Service
The provider gives you a platform to build and deploy applications. You focus on writing code; the provider handles servers, storage, networking, and the operating system. It's like renting a furnished apartment — just move in and start living.
Examples: AWS Elastic Beanstalk, Azure App Service, Google App Engine, Heroku
Best for: Developers who want to focus on code without worrying about infrastructure.
SaaS — Software as a Service
You simply use the software. The provider manages everything from the infrastructure to the application itself. It's like using a hotel — everything is ready, you just check in.
Examples: Gmail, Microsoft 365, Salesforce, Slack, Dropbox
Best for: End users and businesses that want ready-to-use software.