Service models: IaaS, PaaS and SaaS
The cloud isn't one thing. The models differ in how many layers you manage versus the provider. The further down the list, the less you manage and the less you control:
| Model | You rent | Examples |
|---|---|---|
| IaaS: infrastructure as a service | Virtual servers, storage and networking. You install the OS and software. | Amazon EC2 · Azure Virtual Machines · Google Compute Engine |
| PaaS: platform as a service | A ready platform for your code or database; the provider runs the OS and updates. | Azure App Service · AWS Elastic Beanstalk · Amazon RDS · Google App Engine |
| SaaS: software as a service | Ready software you use in a browser. You manage only your data and users. | Microsoft 365 · Google Workspace · Salesforce · Odoo Online · SAP S/4HANA Cloud |
Serverless goes a step further: you write a small function (say, “notify the store when an order ships”), the provider runs it only when called, and you pay per run. Examples: AWS Lambda and Azure Functions.
Watch outA popular analogy: IaaS is renting an empty kitchen and cooking yourself, PaaS is a kitchen stocked with tools and ingredients, and SaaS is ordering the meal ready-made.