Cloud service models explained: IaaS vs PaaS vs SaaS

Cloud computing services are typically delivered through three main service models. Each model defines which parts of the technology stack are operated by the provider and which remain under the customer’s control.    This FAQ explains the differences between infrastructure, platform and software services, and how organisations choose between IaaS, PaaS and SaaS when planning cloud environments. 

Q: What are cloud computing service models?

A: Cloud computing service models describe how different layers of IT infrastructure and applications are delivered as services. The three main models are Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (SaaS). Each model defines who manages the infrastructure, platform components and applications. The more responsibility the provider takes, the less operational management is required from the customer.

Q: What does IaaS mean in cloud computing?

A: Infrastructure as a Service (IaaS) provides virtualised compute, storage and networking delivered through a cloud platform. The provider operates the underlying infrastructure and data centre environment, while customers manage operating systems, applications, identities and data. IaaS is commonly used by organisations that want flexibility and infrastructure control without owning and operating physical hardware.

Q: What is PaaS cloud hosting?

A: Platform as a Service (PaaS) delivers a managed platform environment where developers can build and run applications without managing the underlying infrastructure. The provider manages the operating system, runtime environment, middleware and infrastructure, allowing development teams to focus on application code and deployment.

Q: What is SaaS in cloud computing?

A: Software as a Service (SaaS) delivers complete applications over the internet. Users access the software through a browser or client application while the provider manages the infrastructure, platform, application updates and security controls. Common SaaS examples include collaboration tools, business applications and customer relationship management systems.

Q: What is the difference between IaaS, PaaS and SaaS?

A: The main difference between cloud service models is how operational responsibility is shared.
• IaaS: the provider manages infrastructure while the customer manages operating systems and applications.
• PaaS: the provider manages infrastructure and platform components, while the customer focuses on application development.
• SaaS: the provider manages the full stack, including the application itself, while users simply access the software.

Q: Which cloud service model gives organisations the most control?

A: IaaS provides the greatest level of control because organisations manage the operating system, software environment and application stack. This makes it suitable for workloads that require custom configurations, specific security controls or integration with existing infrastructure.

Q: Which cloud service model requires the least management?

A: SaaS typically requires the least operational management. The provider operates the application and the entire technology stack behind it, allowing organisations to use the software without managing infrastructure, platforms or updates.

Q: When should organisations choose IaaS instead of PaaS or SaaS?

A: IaaS is often chosen when organisations need flexibility to configure infrastructure and applications according to specific operational or security requirements. It can also support workloads that require integration with existing systems or dedicated environments where organisations retain control over operating systems and software configuration.

Q: Can organisations use multiple cloud service models together?

A: Yes. Many organisations operate a mix of cloud service models. For example, business applications may run as SaaS, development platforms may use PaaS, and critical infrastructure workloads may run on IaaS environments. Using multiple models allows organisations to match the right service approach to different operational requirements.