Multichannel stock control that stops the overselling

Stock is the only number in ecommerce that has to be right everywhere at once. Get a price wrong and you lose margin on one order. Get stock wrong and you sell something you do not have, refund a customer who was looking forward to it, and take a hit on the seller metrics that decide whether that marketplace shows you at all.

The failure is not arithmetic, it is timing

You sold the last one on eBay at 9:04. Amazon sold it again at 9:06. Both orders are real, both channels answered correctly at the moment they were asked, and you have one item. Nothing was miscounted — the gap between those two moments is the entire problem.

Closing that gap is what a stock system is for. Not reporting on it afterwards. Closing it.

One record, and only a sale may change it

Qwikr nominates exactly one system as the holder of the stock record and pushes that figure everywhere else within seconds of it changing. The channel that made the sale is never told about its own sale, because it already knows.

The stricter half of the rule matters more: a channel that holds the record hears about sales and nothing else. Not a catalogue import, not a supplier feed, not a bulk edit — those would overwrite the very figures being reconciled against, which is how a well-meaning import wipes out a day of trading.

Movements, not just levels

A stock level tells you what you have. It does not tell you why, and the question that actually gets asked is “who changed this, and when?”

Every change is recorded as a movement with its reason: sold, returned, received, adjusted, damaged, recounted. So a figure that looks wrong can be walked backwards to the event that made it wrong, which is the difference between fixing a problem and arguing about it.

When a sale exceeds what you have

Sometimes it happens anyway — a marketplace that was slow to hear, a count that was wrong before Qwikr ever saw it. The order is still recorded, the level is floored at zero rather than going negative, and the event is logged with the SKU, the channel, the shortfall and what it most likely means.

Floored and logged beats blocked and silent. An order you refused to record is an order you cannot fulfil and cannot explain.

The rest of the operation

Purchase orders, suppliers, goods-in and multiple warehouses all exist for the same reason: they are where stock comes from and where it physically is. They feed the same figure the channels read, which is the only reason they are worth having in the same system.