A Kubernetes-native config-overlay tool, the way most GitOps teams template environment differences without templating engines.
Kustomize is a Kubernetes config-management tool, built into kubectl, that uses overlays to represent environment differences (dev, staging, prod) without text-template substitution. Bases hold the common manifests; overlays patch them with environment-specific values (replica count, image tag, secrets). The output is plain YAML that can be diff'd, version-controlled, and applied through GitOps. Helm covers similar ground via templating; many teams now use both, Helm for third-party charts, Kustomize for first-party.
Without Kustomize or Helm, Kubernetes environments either drift apart (each is hand-edited) or get a homegrown templating engine (which inevitably becomes the team's least-loved internal tool). Kustomize's overlay model is the pragmatic middle path, no templating hell, full transparency, easy review.
See the part of the platform that handles kustomize in production.