What You Are Actually Buying (IaaS vs PaaS vs SaaS)

Why this matters

Every conversation about cloud architecture eventually hinges on which layer you are buying. If you cannot tell IaaS from PaaS from SaaS you will end up paying for managed services you did not need, or running raw VMs when a managed runtime would have shipped you in a week. Knowing where each provider draws the line is the first filter you apply when picking a service.

Demo

List a representative service from each layer on AWS and Azure to see the boundary in concrete terms.

Try it yourself

1. Run the AWS describe-instance-types call and note that you are told vCPU and memory but nothing about the OS image — that is the IaaS boundary.
2. Filter the Beanstalk solution stacks for Node.js 20 and observe that the OS, web server, and runtime are all bundled — that is what PaaS sells you.
3. On Azure, change the App Service runtime filter from NODE to PYTHON and confirm the same managed-runtime contract holds across languages.

References

• NIST SP 800-145 — Definition of Cloud Computing
• AWS — Types of Cloud Computing