IaaS, PaaS, and SaaS are the three layers of cloud services. Understanding the difference helps you choose the right tool and have better architecture conversations.
The easiest way to understand the three models is the pizza analogy:
| Layer | On-Premises | IaaS | PaaS | SaaS |
|---|---|---|---|---|
| Application | You | You | You | Provider |
| Data | You | You | You | Provider |
| Runtime | You | You | Provider | Provider |
| OS | You | You | Provider | Provider |
| Virtualization | You | Provider | Provider | Provider |
| Servers | You | Provider | Provider | Provider |
| Storage | You | Provider | Provider | Provider |
| Networking | You | Provider | Provider | Provider |
You get virtual machines, storage, and networking. You install and manage everything on top.
You control: OS, runtime, middleware, apps, data Provider controls: Physical hardware, virtualization, networking
# IaaS example — AWS EC2
# You provision a VM and do everything yourself
ssh ec2-user@your-server.amazonaws.com
sudo apt install nodejs
git clone your-app
npm install && npm start
# You manage: updates, security patches, scaling, monitoringBest for:
Examples: AWS EC2, Google Compute Engine, Azure VMs, DigitalOcean Droplets
You deploy your code. The platform handles everything else — runtime, scaling, patching.
You control: Application code and data Provider controls: Everything else
# PaaS example — Vercel
# You just push code, platform handles the rest
git push origin main
# Vercel automatically: builds, deploys, scales, manages SSL, CDNBest for:
Examples: Vercel, Heroku, AWS Elastic Beanstalk, Google App Engine, Railway, Render
You use the software via a browser or API. You manage nothing.
You control: Your data and configuration Provider controls: Everything
# SaaS example — using GitHub
# You just use it — no servers, no maintenance
git push origin main
# GitHub handles: servers, storage, backups, security, uptime
Best for:
Examples: Gmail, Slack, GitHub, Salesforce, Notion, Figma, Stripe
| Model | Upfront cost | Operational cost | Expertise needed |
|---|---|---|---|
| On-premises | Very high | High (staff, maintenance) | High |
| IaaS | None | Medium (you manage VMs) | Medium-High |
| PaaS | None | Low-Medium | Low-Medium |
| SaaS | None | Low (subscription) | Low |
A typical startup uses all three:
SaaS: GitHub (code), Slack (comms), Notion (docs), Stripe (payments)
PaaS: Vercel (frontend), Railway (backend API)
IaaS: AWS S3 (file storage), AWS RDS (database)
You don't have to pick one — use the right model for each component.