Certified - CompTIA IT Fundamentals+

In this episode, we explore the three core service models that form the foundation of cloud computing: Software as a Service, Platform as a Service, and Infrastructure as a Service. These models—often abbreviated as SAAS, P A A S, and I A A S—define how cloud providers and customers share responsibility for delivering, managing, and securing technology resources. For anyone preparing for the ITF Plus exam, understanding these models is essential to identifying cloud roles, recognizing service examples, and distinguishing levels of control.
This topic is part of Domain Two of the ITF Plus exam, which includes cloud and virtualization technologies. You may encounter questions that ask you to match cloud services to their definitions, select the right model based on a scenario, or identify the correct service level for a given function. The exam focuses on conceptual understanding—not on how to configure, price, or deploy cloud tools. If you know who manages what, and you can match examples to service types, you're well-positioned to succeed.
Cloud computing refers to the use of remote servers over the internet to deliver IT services on demand. Instead of managing physical servers in a data center, cloud customers access services through browsers, apps, or programming interfaces. Cloud computing eliminates the need for large capital investment in hardware and shifts many IT responsibilities to service providers. The services offered can include storage, processing power, applications, and full system environments.
The three core service models—SAAS, P A A S, and I A A S—represent different layers of responsibility in cloud delivery. Each model defines what the provider offers and what the customer must manage. At the top layer, SAAS requires minimal user management. In the middle, P A A S gives developers the tools they need while handling infrastructure. At the base, I A A S gives full control to the customer over virtual machines and resources.
Software as a Service, or SAAS, delivers applications through a web browser or mobile app. The user does not install, update, or manage the application; everything is handled by the provider. Common examples include Google Workspace, which includes Gmail and Google Docs, or Microsoft Three Sixty-Five, which offers Word, Excel, and Teams online. The user simply logs in and starts working.
The key features of SAAS include simplicity, scalability, and full management by the vendor. The user interacts only with the software’s interface, while the cloud provider handles servers, operating systems, updates, backups, and security. This model is ideal for tasks like email, document creation, video conferencing, and customer relationship management, where fast access and minimal overhead are essential.
Platform as a Service, or P A A S, provides a framework and tools for developers to build, test, and run their own applications. The platform includes pre-configured environments, databases, and runtime engines, but the developer supplies the application code. Examples of P A A S include Google App Engine and Microsoft Azure App Services. These platforms eliminate the need to manage servers or install operating systems.
With P A A S, developers manage the application’s functionality while the provider manages the infrastructure beneath it. This model is well-suited for development teams that want to focus on writing code rather than managing hardware. P A A S is particularly popular in software development environments, where rapid deployment and scalability are important but system-level control is not required.
Infrastructure as a Service, or I A A S, delivers the raw computing building blocks—virtual machines, storage, and networking—on a pay-as-you-go basis. In this model, the cloud provider supplies the infrastructure, and the customer installs and manages the operating system, software, and configuration. Examples of I A A S include Amazon Elastic Compute Cloud, known as E C Two, and Microsoft Azure Virtual Machines.
I A A S provides maximum flexibility and control, allowing IT professionals to replicate entire data centers in the cloud. It is best suited for companies that have the expertise to manage complex environments or need to run customized workloads. I A A S customers are responsible for updates, security patches, performance tuning, and system backups, making it a powerful but demanding option.
To compare the three models, think in terms of control versus convenience. SAAS offers the least control but the greatest simplicity—just log in and use the software. P A A S balances control and convenience—developers handle code, but the platform handles infrastructure. I A A S gives full control over the environment but requires technical skill to manage all aspects. Understanding this spectrum is critical for choosing the right service model for a scenario.
The level of ownership and responsibility differs across all three service models. In Software as a Service, the cloud provider owns and manages the entire stack, from infrastructure to application updates. In Platform as a Service, the provider offers a ready-to-use environment for application development, but the customer owns the application code and its behavior. In Infrastructure as a Service, the provider only supplies the hardware, and the user is responsible for everything else—operating system, security, software, and maintenance.
Each model aligns with specific use cases depending on the organization's needs. Software as a Service is perfect for businesses needing email, word processing, or collaboration tools with minimal technical management. Platform as a Service is ideal for developers who want to build and deploy apps without worrying about server administration. Infrastructure as a Service is chosen by organizations that require full control over their environment, such as custom server configurations, legacy app hosting, or testing enterprise deployments.
Scalability is a common benefit shared by all three cloud models. Whether you're using Software as a Service for file storage or Infrastructure as a Service for running virtual machines, cloud platforms are designed to scale based on demand. With Infrastructure as a Service, scaling often involves adjusting virtual hardware settings. In Platform as a Service, scaling can be as simple as changing configuration parameters. With Software as a Service, scaling is usually built-in and automatic, such as when adding more users to an email platform.
Billing for cloud services typically follows a subscription or pay-as-you-go model. Software as a Service is usually billed monthly or annually, depending on features and user count. Platform as a Service and Infrastructure as a Service often charge based on usage, including the number of virtual machines, storage, bandwidth, or compute time. This pricing model allows businesses to only pay for what they use and adjust costs as their needs evolve.
Cloud service accessibility varies slightly between the three models. Software as a Service is commonly accessed through web browsers or dedicated apps and is meant to be intuitive and user-friendly. Platform as a Service and Infrastructure as a Service generally involve more technical access, often using web dashboards, command-line interfaces, or remote desktop tools. All models require reliable internet access and user authentication for secure entry into the platform.
Security responsibilities are divided differently across the models. In Software as a Service, the provider is responsible for almost all security layers, from physical servers to application logic. In Platform as a Service, security is a shared responsibility: the provider secures the platform, while the user is responsible for the application and its data. In Infrastructure as a Service, users must secure their virtual machines, operating systems, and all the software they run. Understanding these boundaries is important for setting policies and managing risk.
The ITF Plus exam frequently tests your ability to recognize cloud models through real-world examples. For instance, a question may describe a user logging into a web-based application—this points to Software as a Service. A developer deploying code to a managed platform points to Platform as a Service. A scenario involving the setup of virtual machines, firewall rules, and storage volumes is likely to be Infrastructure as a Service. Matching definitions to examples is a core exam skill.
The exam does not require you to deploy or configure any cloud services. You won’t need to set up a virtual machine, calculate billing rates, or configure load balancers. The focus is entirely on understanding the roles, definitions, and characteristics of each model. You should be able to identify who manages what in each model and determine which service best fits a given business or technical goal.
Cloud models are not just important for the ITF Plus exam—they form the base for nearly every modern technology deployment. Understanding them supports learning in more advanced certifications, such as Security Plus, Cloud Plus, and C Y S A Plus. Knowing the difference between models also helps you communicate with vendors, support users in a hybrid environment, and make recommendations about which tools best fit a user’s needs or a company’s budget.
To wrap up, cloud service models divide the responsibilities of infrastructure, platforms, and applications between the provider and the customer. Software as a Service is the simplest to use, requiring no setup. Platform as a Service gives developers a place to work without worrying about hardware. Infrastructure as a Service offers full control but demands technical management. Knowing which model to choose—and what each one provides—is essential for both exam success and career readiness.