Cloud Service Models: IaaS, PaaS, and SaaS
Cloud computing services are categorized into three main service models based on the level of management provided by the vendor and the level of control retained by the user.
1. IaaS (Infrastructure as a Service)
IaaS is the most flexible and fundamental cloud service model. The vendor provides virtualized infrastructure resources like servers, storage, and networking.
| Feature | Description | Analogy |
|---|---|---|
| Provided | Virtual Machines (VMs), Storage, Networks, OS Hypervisor | Renting the land and walls to build a house |
| User Responsibility | Operating System (OS), middleware, applications, runtime environments. | Must manage and maintain the OS and all software layers. |
| Examples | Amazon EC2, Microsoft Azure VM, Google Compute Engine |
2. PaaS (Platform as a Service)
PaaS provides the platform—the hardware and software environment—necessary for developing, running, and managing applications. Developers focus purely on coding and data.
| Feature | Description | Analogy |
|---|---|---|
| Provided | IaaS + OS, Middleware, Development tools, Database management | Renting a fully furnished apartment |
| User Responsibility | Application code and application data only. | No need to worry about server maintenance or OS patching. |
| Examples | Google App Engine, AWS Elastic Beanstalk, Heroku |
3. SaaS (Software as a Service)
SaaS delivers the entire software application over the internet, typically on a subscription basis. The user only needs a web browser to access the service.
| Feature | Description | Analogy |
|---|---|---|
| Provided | Everything (Infrastructure, Platform, Application, Data) | Staying in a hotel room |
| User Responsibility | None (only using the software) | Login and immediately start using the service. |
| Examples | Gmail, Microsoft 365, Salesforce, Slack |