Which cloud computing service model sits between IaaS and SaaS?

The cloud computing service model that sits between Infrastructure as a Service (IaaS) and Software as a Service (SaaS) is Platform as a Service (PaaS). PaaS provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the underlying infrastructure typically associated with IaaS.

PaaS facilitates the deployment of applications by offering development tools, middleware, database management systems, and business analytics, which developers can use to create applications without dealing with the hardware or network configurations involved in IaaS. Unlike SaaS, which delivers software applications directly to end-users, PaaS focuses on providing a framework that developers can build upon.

Thus, PaaS serves as a bridge, integrating the bare metal and virtualized resources of IaaS with the end-user-ready applications provided by SaaS, making it an essential component in the cloud service spectrum.