Service Models Intro
Understand the core difference between IaaS, PaaS, and SaaS using the 'Who Manages What' mental model.
This lesson is purely conceptual — no AWS usage required.
The core mental model
The difference between IaaS, PaaS, and SaaS is mainly:
How much you manage vs how much the provider manages.
A helpful rule:
- More control = more responsibility
- More convenience = less control
The three models
Definition Guide
IaaS, PaaS, and SaaS
Each model draws the line between what you manage and what the provider manages at a different layer.
SaaS — Software as a Service
Meaning
You use a complete software product online. The provider runs everything behind it.
You manage
- Your account settings
- Your data inside the app (what you upload, create, share)
- How you use the product
Provider manages
- The app, servers, scaling, updates, uptime, most security controls
Examples
Email service, online docs editor, CRM tools.
When it's ideal: When you want the outcome (use the software), not the engineering.
PaaS — Platform as a Service
Meaning
You deploy your code to a managed platform that handles much of the infrastructure.
You manage
- Your application code
- Your app configuration (settings, environment variables)
- Your data and access rules
Provider manages
- Much of the infrastructure
- Often the runtime, scaling, patching, and load handling (depending on the service)
Examples
Managed app hosting platforms, managed databases, managed API platforms.
When it's ideal: When you want to build an app, but not manage servers and OS updates.
IaaS — Infrastructure as a Service
Meaning
You rent raw infrastructure: virtual servers, networking, storage.
You manage
- The operating system (often)
- Patching and security configuration
- Installing runtimes and dependencies
- Your application code and deployments
Provider manages
- Physical data centers
- Physical hardware
- Basic underlying virtualization and infrastructure
Examples
Virtual machines, virtual networks.
When it's ideal: When you need deep control over the system or custom setups.
Micro-activity
Sort the examples
Label each item as IaaS, PaaS, or SaaS.
A hosted email inbox you log into via a browser
A platform where you upload your web app code and it deploys it for you
A rented virtual machine where you install everything yourself
An online document editor you use without deploying any code
A managed database where you do not install or patch the database software yourself
A managed "run my code" service where the provider handles scaling and servers
0 of 6 matched so far.
Common confusion
Is PaaS always easier than IaaS?
Can one product include multiple models?