Inventory Reservation
Definition
Inventory reservation is the practice of holding stock for an order while payment is in progress, so two customers cannot buy the last unit at the same time. Reserved units are subtracted from sellable stock but not yet from physical stock. If the payment fails or times out, the reservation is released and the units are sellable again.
Why it matters for your store
Between "pay now" and "payment confirmed" there is a gap of a minute or more, filled by 3-D Secure. During a sale, two customers can enter that gap for the same last unit. Without a reservation, both pay and one is refunded with an apology. With one, the second customer is told the item is gone before they reach the bank.
Reservations also need to expire. A held unit that never releases is stock you cannot sell. The hold should last long enough for a real payment and no longer, and a failed payment should release it at once.
How Kambloo handles it
Kambloo reserves stock at the moment the customer confirms payment, not when they add to cart. The order is created and the reservation made in one database transaction, with row locks taken in a fixed order so concurrent checkouts cannot deadlock. Sellable stock is physical stock minus reservations.
Card reservations expire after 30 minutes, enough to cover 3-D Secure. Bank transfer reservations last 24 hours by default, adjustable per store. A job runs every minute to release expired holds and mark the order as timed out. A failed or declined payment releases the hold immediately, so the customer can retry without blocking the unit.
Marketplace orders reserve from the same pool, and cash on delivery orders convert the reservation to a deduction at order time. If a late bank confirmation arrives after a hold expired, stock is rechecked and the order either completes or is held for your review.
Questions about Inventory Reservation
Does adding an item to the cart reserve it?
Not on Kambloo. Stock is reserved when the customer starts paying, so browsers with full carts do not block stock for hours. The reservation lasts long enough to complete 3-D Secure.
What happens if the bank confirms a payment after the reservation expired?
Kambloo checks stock again. If it is available, the order completes normally. If not, the order is held for the merchant to resolve by supplying the item or refunding. The customer is never charged silently for nothing.