IaaS vs PaaS vs SaaS — Cloud Service Models Explained

IaaS vs PaaS vs SaaS Explained

1 min readPublished 22 Jul 2026

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Cloud service models describe how much of the stack the provider manages versus how much you do. It's the single most important cloud concept — and a guaranteed interview question.

Interactive explainer

Cloud Service Models: IaaS, PaaS & SaaS

How much of the stack you manage — and how much the provider does.

Tap or hover a part to learn more.

On-premises

You manage everything.

In a traditional data centre you own and manage the whole stack — hardware, virtualisation, OS, runtime and the application. Maximum control, maximum operational burden.

Check your understanding

1. With IaaS, who patches the guest operating system?

2. Microsoft 365 is an example of…

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Cloud Service Models Cloud Security CompTIA Security+

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The three models

IaaS (Infrastructure as a Service) — VMs, storage and networking (Azure VMs, AWS EC2). You manage the OS upwards. Most control.
PaaS (Platform as a Service) — deploy code without managing the OS (Azure App Service, AWS Elastic Beanstalk). Less control, far less overhead.
SaaS (Software as a Service) — finished applications you just use (Microsoft 365, Salesforce). Least effort.

Why it matters

The service model decides your operational workload and — through the shared responsibility model — what you must secure. Choosing PaaS over IaaS can remove huge amounts of patching and maintenance.

Applies directly to Azure, AWS and Security+.

Interview Intelligence

How this topic actually shows up in interviews — and how to demonstrate you understand it.

Why employers ask about this

It's the most common cloud interview question and underpins security responsibility. Employers check you can reason about trade-offs, not just recite definitions.

Technical questions

Explain IaaS, PaaS and SaaS with an example of each.+

IaaS = Azure VM/EC2 (you manage OS up); PaaS = App Service/Beanstalk (deploy code); SaaS = Microsoft 365 (just use it).

Behavioural questions

Describe choosing a managed service over self-hosting.+

STAR: the requirement, choosing PaaS to cut ops overhead, and the reliability/time benefit.

Real-world scenarios

“A small team must run a web app but has no time to manage servers.”+

Expected answer: Recommend PaaS to remove OS management, noting reduced control and any lock-in.

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Employability Intelligence

Where this knowledge takes you — the jobs, skills and certifications it feeds into.

Relevant roles

Cloud EngineerAzure AdministratorAWS Solutions Architect

Skills you're proving

Service modelsTrade-off analysisCloud security basics

Recommended certifications

CompTIA Security+

Career progression

Cloud Fundamentals → Azure/AWS pathway → Cloud Engineer/Architect.

What employers expect

That you understand cloud concepts well enough to be productive and safe on Azure or AWS from day one.

Frequently asked questions

What's the easiest way to remember IaaS/PaaS/SaaS?

IaaS = you manage the OS up; PaaS = you manage the app and data; SaaS = you manage only your data and users.

Is a VM IaaS or PaaS?

A virtual machine is IaaS — you manage the operating system and everything above it.

Which model has the least management overhead?

SaaS — the provider manages essentially everything except your data and access.

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Missiora is an AI Employability Intelligence platform. Our resources are researched and reviewed by the Missiora team to help you measure, improve and prove your career readiness.