Cloud Service Models: IaaS, PaaS, SaaS

Cloud services are typically categorised into three models, each handing off a different amount of management responsibility from the customer to the provider.

The Three Models

As you move from IaaS to PaaS to SaaS, the provider manages progressively more of the technology stack, and the customer retains progressively less control but also less operational burden.

• IaaS (Infrastructure as a Service) — rents virtual machines, storage, and networking; you manage the OS and everything above it. Example: Amazon EC2.
• PaaS (Platform as a Service) — provides a managed platform for running applications, handling the OS and runtime for you. Example: Google App Engine, Azure App Service.
• SaaS (Software as a Service) — delivers a complete, ready-to-use application over the internet. Example: Gmail, Salesforce, Microsoft 365.

Choosing a Model

IaaS suits teams who need maximum control over their environment. PaaS suits developers who want to focus purely on writing application code without managing servers. SaaS suits end users and businesses who simply need a working application, with no development involved at all.

Common Mistakes

• Choosing IaaS when a team's actual goal is simply to run an application quickly, taking on unnecessary infrastructure management overhead.
• Assuming SaaS applications require no configuration or oversight at all — user management, permissions, and data handling still need attention.
• Confusing PaaS (a platform for building on) with SaaS (a finished, ready-to-use application).
• Not considering vendor lock-in, which tends to increase as you move from IaaS toward more managed, provider-specific PaaS and SaaS offerings.