Not Expired ≠ Authorized

Expiry is a fact. Authorization is an outcome.

This note describes a semantic boundary that is easy to blur in production systems.

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Boundary

ExpirySignal can emit: expired / not expired.

Your system decides what to do with that signal at an enforcement point.

A user being not expired does not imply they are allowed to do anything.

Invariants

Not expired ≠ permitted
Not expired ≠ authenticated
Not expired ≠ paid
Not expired ≠ safe

Signals remain facts even when you wish they were enforcement.

Failure modes

Clock skew causes “not expired” to read incorrectly
Stale reads cause “not expired” to persist after expiry
Developers treat “not expired” as an allow-list

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