Definition. A model that describes not how a state is reached but which state should exist, e.g. “three pods of this type, with this resource limit, behind this service”. Tools such as Kubernetes, Terraform and Crossplane converge on this desired state and maintain it.

Why it matters. Imperative scripts are hard to undo and hard to repeat. Declarative infrastructure is a prerequisite for GitOps, reproducible environments and disaster recovery that does not depend on individual people.

Related. GitOps, Immutable Infrastructure, Platform Engineering