Session capacity

Session capacity is the number of clients one appointment slot can hold. A one-to-one service has a capacity of one. A class or shared session has more, and stays bookable until every seat is taken.

Also called: seats, group booking, class size

Capacity is what separates a class from an appointment. Without it, a group session either has to be booked as a single appointment by one person, or the slot closes as soon as one client takes it.

The subtlety is that capacity must be enforced where bookings are written, not where they are displayed. Two clients taking the last seat at the same moment is a race that only the database can settle.

In Booked a service defines how many seats a sitting holds, and the constraint that prevents overlapping bookings understands seats, so the last seat can only be sold once.