What are the three cloud service models used in healthcare?

The three models are: Infrastructure as a Service (IaaS) — providing virtualised compute, storage, and networking with the organisation managing OS and applications (e.g. AWS EC2); Platform as a Service (PaaS) — a managed environment for developing and deploying applications without managing infrastructure (e.g. Azure App Service); and Software as a Service (SaaS) — complete applications delivered over the internet with the provider managing everything (e.g. Microsoft 365, cloud-hosted EHR modules). SaaS offers fastest deployment but least customisation; IaaS offers maximum control.