The double booking that cannot happen

Two requests arriving in the same millisecond both read an empty calendar and both look fine. Checking before writing narrows that window and never closes it, so the overlap is refused by a constraint inside the database itself — the one place a decision can be made that another request cannot get in front of.

One party leaves on the fifth and the next arrives on the fifth. That is the ordinary day in every business that works this way, and a system treating it as a clash costs a night's revenue on every single changeover.

Which van somebody gets is a business decision — spread the mileage, keep the automatic back for whoever needs it, give the good flat to the long booking. Picking the first free row on your behalf silently imposes one of those policies on everybody.

An unbookable two days between a Friday return and a Monday pickup is revenue nobody can see from a list of bookings. Those holes are surfaced as dates you could sell, rather than as a utilisation percentage that supports no action at all.