What Is Platform as a Service (PaaS)?
A company develops a custom web application that requires a specific runtime environment and middleware. The company wants to avoid managing the underlying servers, operating system patches, and runtime scaling. They choose a cloud service where they can upload their application code and the provider automatically handles the OS, runtime, and scaling based on demand. Which cloud service model does this describe?
⚠ Common exam trap
CompTIA often tests the distinction between IaaS and PaaS by describing a scenario where the customer manages the OS but not the hardware, leading candidates to mistakenly choose IaaS when the provider actually handles the OS and runtime.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Platform as a Service (PaaS)
This scenario describes Platform as a Service (PaaS), where the cloud provider manages the underlying infrastructure, operating system, runtime environment, and middleware. The customer only needs to upload their application code, and the provider automatically handles scaling, patching, and runtime dependencies. This contrasts with IaaS, where the customer manages the OS and runtime, and SaaS, where the provider delivers a fully functional application.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Infrastructure as a Service (IaaS)
Why it's wrong here
IaaS provides virtualized hardware (e.g., VMs, storage) but the customer is responsible for managing the operating system, runtime, and middleware. The scenario describes a service that manages these components automatically, so IaaS is not the best fit.
- ✓
Platform as a Service (PaaS)
Why this is correct
PaaS delivers a platform (OS, runtime, middleware) for customers to deploy their own applications. The provider manages the underlying infrastructure, patches, and scaling. This matches the scenario where the company uploads code and the provider handles the rest.
- ✗
Software as a Service (SaaS)
Why it's wrong here
Software as a Service delivers fully functional, ready-to-use applications over the internet, typically accessed via a browser, where the provider manages the entire application stack including the OS, runtime, middleware, and application itself. Since the company is uploading and deploying custom code, SaaS is not applicable because it offers no mechanism to host or run bespoke applications — the customer only consumes the pre-built software and has no control over the runtime environment or platform.
- ✗
Desktop as a Service (DaaS)
Why it's wrong here
Desktop as a Service provides virtualized user desktops, delivering a complete desktop operating system and environment to end-user devices over the network, but it is not designed for hosting custom web application code. It focuses on endpoint computing, not on running server-side middleware or application runtimes, so it cannot meet the requirement of managing the runtime and scaling for a company's custom application. In cloud service taxonomy, DaaS is essentially a variant of VDI for user access, entirely orthogonal to platform hosting.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
Go deeper
Related to this question
Learn chapter
Public, Private, Hybrid, Community Cloud
Key term
Software as a Service
Software as a Service (SaaS) is a cloud computing model where users access software applications over the internet on a subscription basis, without installing or maintaining the software locally.
Key term
Anything As A Service
A model where you rent any IT resource or service over the internet instead of owning it.
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