Which of the following is not a cloud service model?

Question

Accepted Answer

The correct option is (4):
The cloud computing industry has three fundamental, universally accepted service models, often referred to as the 'cloud stack': Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). **System-as-a-service** is a term that does not correspond to any official or industry-standard cloud service model. While other specialized models exist, such as CaaS (Containers as a Service) or FaaS (Functions as a Service), 'System-as-a-service' is not a recognized or defined category within the common cloud architecture. It is presented here as a distractor to test your knowledge of the established service model nomenclature. Since the question asks for the option that is *not* a cloud service model, this term is the correct choice.

The incorrect option is (1):
Infrastructure as a Service (IaaS) is one of the three primary and foundational cloud service models. IaaS is the most basic layer, giving the customer the highest level of control, as it provides fundamental computing resources like virtual machines, networks, storage, and operating systems over the internet on a pay-as-you-go basis. The customer is responsible for managing the operating system, applications, and data, while the cloud provider manages the underlying physical infrastructure and virtualization layer. This model is commonly used for hosting websites, testing and development environments, and large-scale data analysis.

The incorrect option is (2):
Platform as a Service (PaaS) is a core cloud service model that sits above IaaS in the cloud stack. PaaS provides a complete environment for developing, running, and managing applications without the complexity of managing the infrastructure, such as the servers, operating systems, and storage. It offers a framework for developers, allowing them to focus exclusively on coding and deployment. The cloud provider handles the operating system and runtime environment, while the user manages the application and data. This model significantly speeds up the application development and deployment lifecycle.

The incorrect option is (3):
Software as a Service (SaaS) is the most complete and familiar cloud service model, residing at the top of the cloud stack. SaaS delivers an entire, ready-to-use application over the internet, typically on a subscription basis, which the user accesses via a web browser or client application. In the SaaS model, the cloud provider manages the entire application stack, including the software, data, operating system, and all underlying infrastructure. Examples include popular web-based email services and CRM tools. The user is only responsible for using the software itself.