Stock reservations
Stock held while a customer is paying, so two people cannot buy the last one.
There is a gap between someone starting checkout and their payment clearing. It is short, and on a busy product it is long enough for a second customer to buy the same last item.
How it works
- Entering checkout reserves the stock against that cart.
- The reservation expires if the order is not completed, returning the stock rather than stranding it.
- A completed order converts the reservation into a real decrement.
The trade-off, stated plainly
Reservations cost you availability. Stock held for an abandoned checkout is stock nobody else could buy for the duration, and a long expiry on a fast-moving product will suppress sales you would otherwise have made.
Short expiries are almost always right. The failure being prevented — taking money for something that is gone — is worse than the failure being introduced, but only if the window is measured in minutes.
What it does not do
It does not reserve across marketplaces. A marketplace does not tell you someone is at its checkout, so a reservation here cannot protect against a simultaneous Amazon sale. That is what the source-of-truth rule and prompt propagation are for.
Stop reconciling stock by hand
One catalogue, six channels, one stock figure that stays right.