eBay Amazon integration that keeps one stock count across both marketplaces

eBay and Amazon are both marketplaces, and a marketplace only knows about the orders placed on it. Neither can be handed a sale that came from the other and asked to pick, pack and post it. That is how both platforms are built rather than a gap in what we do, and it is the first thing to settle before you plan a workflow around this pair.

What is left is the part that causes real trouble: one pile of stock, two listings and no shared count between them. QuickSync sits in the middle and corrects each side from the other. A sale on eBay lowers what Amazon shows, and for items you post yourself an Amazon sale does the same the other way. Orders from both marketplaces land in QuickSync, so you are not reconciling two dashboards by eye.

One side of this pair runs on a timer. eBay has no way to announce a sale, so it gets asked instead: every couple of minutes, stock and orders together. That is a short window rather than no window at all, and on the lines you sell fastest a unit or two of headroom is the cheap way to cover it while you get on with something else.

Items pair up by SKU, so the shorter of the two limits is the one you have to design to. eBay will hold 50 characters. Amazon takes 20, which is the tighter limit in this pair by some distance. A SKU that fits eBay comfortably can still arrive at Amazon shortened, and a shortened SKU no longer matches the item it came from.

Nothing errors when this happens, which is what makes it awkward. We truncate at the channel’s limit rather than refusing to send, so the connection stays green and the item simply stops pairing with itself. You find out weeks later when one count has drifted away from the other. Twenty characters goes quickly if your SKUs are built out of words, so sort by length and look at the top of the list first.

Two more Amazon rules to plan around. We always send your count out to Amazon, but we only take changes back for items you ship yourself; stock Amazon holds and ships keeps its own count, deliberately, because Amazon knows what is on its own shelves. And Amazon has no field for a tracking number, so we cannot write one back. Tracking stays in QuickSync.