Backend & systems·API and interface design
you announce the endpoint is going away, keep it running for six months, and watch the traffic to find out who is still on it.
Deprecation window
Also calledsunset period, Sunset header
The published period between announcing a removal and performing it. Its real job is instrumentation: you cannot retire anything you cannot measure usage of, per caller. Deprecating without per-client traffic attribution means the window ends and you still cannot safely turn it off.