Availability

Availability is the set of times a client can actually book. It is computed from opening hours, staff working hours, service duration, buffers, minimum notice, the booking window, time off, and appointments already taken.

Also called: open slots, bookable times, free slots

Availability is derived, never stored. Every input — an added appointment, a staff member's day off, a changed buffer — changes it, so anything cached goes stale the moment the schedule moves.

It must also be computed on the server. A client's browser can be paused, stale, or edited, so a slot that looks free on screen proves nothing about whether it can be booked.

Booked recalculates availability from the schedule on every request and validates it again when the booking is written.