Platform as a Service (PaaS)

A hosting model where the provider runs the servers, operating system, and deployment tooling, so you supply application code and configuration rather than infrastructure.

PaaS sits between renting virtual machines, where you own every layer above the hypervisor, and serverless functions, where you give up long-running processes and control over the runtime. The trade is deliberate: you accept the platform's opinions about how apps are built and deployed, and in exchange you stop maintaining base images, patching kernels, and wiring up load balancers.

The practical test of a PaaS is what happens on a bad day. Does it tell you why a deploy failed, let you roll back in one step, and keep the previous version serving while the new one starts?