Service Models: IaaS, PaaS, SaaS
Not all cloud is the same amount of cloud. There's a ladder — from renting raw machines and doing everything yourself, up to using finished software that just works. Three rungs of that ladder have names you'll hear constantly: IaaS, PaaS, and SaaS.
They sound technical, but the idea behind them is simple and worth getting straight early: each rung is a different answer to one question — how much do you want to manage yourself, and how much should the provider handle?
Pizza makes it concrete. You can make one from scratch at home, buy a ready-made base and just bake it, or order delivery and do nothing but eat. Same dinner, three levels of "done for you" — and that's exactly the IaaS, PaaS, SaaS ladder.
IaaS — Infrastructure as a Service
At the bottom rung you rent the raw building blocks: machines, storage, networking. The provider keeps the hardware running; everything built on top — the operating system, the software, the updates — is yours to manage. Most control, most work. This is the "make the pizza from scratch" option.
PaaS — Platform as a Service
A rung up, you bring just your own application and hand the rest to the provider — the machines, the operating system, and the plumbing underneath all run for you. You focus on your software, not on the computers it sits on. That's the ready-made base: you add your toppings, they handle the oven.
SaaS — Software as a Service
At the top, you don't manage anything — you just use finished software over the internet. Email like Gmail, file storage like Dropbox, business tools like Salesforce: all SaaS. Someone else runs every layer; you simply log in and use it. This is ordering delivery — you only enjoy the result.
The Trade Up the Ladder
Moving up the ladder, you give up control and gain convenience: less to manage, less that can go wrong, but fewer knobs to turn. The right rung depends on how much control you actually need. Most organizations use all three at once — SaaS for email, PaaS to run an app, IaaS where they need full control.
- "IaaS, PaaS, and SaaS are products you choose between." They're layers, not rivals. Most organizations use all three at the same time for different jobs.
- "SaaS isn't really 'the cloud'." It's the most-used cloud of all — every web app you log into is SaaS running on a provider's machines.
- "Higher up the ladder is always better." More convenience means less control. The right rung depends on how much you need to manage yourself; sometimes that's a lot.
- IaaS, PaaS, and SaaS are the words every cloud conversation uses to say "who manages what" — knowing them lets you follow almost any discussion.
- The ladder reappears throughout the course: serverless, managed databases, and more are all really "move up a rung, let the provider do more".
- It helps you judge a real choice — how much control a team keeps versus how much work it offloads — which is a decision managers weigh constantly.
Knowledge Check
What single question do IaaS, PaaS, and SaaS each answer differently?
- How much you manage yourself versus how much the provider handles
- Which country your data is physically stored in
- Whether the cloud service is free to use or something the customer has to pay for each month
- Which of the three providers happens to be the largest
Gmail, Dropbox, and Salesforce are examples of which model?
- SaaS — finished software you simply log in and use
- IaaS — raw machines and storage you build everything on yourself
- PaaS — a platform you bring your own application to and deploy
- None of these — they aren't really cloud services at all
With PaaS, what does the provider handle and what do you handle?
- You bring your app; the provider runs the machines and everything under it
- You manage the operating system and software stack yourself on a raw rented cloud machine
- You manage nothing and simply use a finished, ready-made product
- You buy and own the physical hardware the platform runs on
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