By the Just Create App team

A health endpoint becomes useful when a team agrees what a failed response should do. Should traffic stop? Should a container restart? Or should the application have more time to finish starting?

Kubernetes gives those questions separate names: startup, readiness and liveness. They are not three interchangeable ways to ask whether a port is open. This documentation-based guide explains the decision before the configuration. It is not a production test, a deployment recipe or a claim of measured availability.

Write the failure action before the endpoint

A probe is a periodic diagnostic performed by the kubelet. The Kubernetes probe documentation describes checks that execute code in a container or make a network request.

The distinction that matters is the response to failure:

A startup probe allows time for initialization. When one is configured, liveness and readiness probes do not run until it succeeds.…