Why a single number oversells

Publishing the same available quantity to three channels means three customers can buy the last unit in the seconds before any of them syncs back. The faster the channels, the worse it gets.

Per-channel buffers

Hold back a small quantity per channel, sized to that channel’s sales velocity and sync latency. A fast marketplace with a slow feed needs a larger buffer than your own storefront with a webhook.

Allocation order and measurement

Decide explicitly which channel is allocated first when stock is tight, and track oversell rate as a metric per channel so you can tell whether a buffer change actually helped rather than just feeling safer.