Five sales channels are not five stores. They are one inventory that has to tell the same truth in five places at once, or you sell what you do not have.

We started by naming the source of truth. The store owns stock; the channels reflect it. Every marketplace listing became a read of one number, never a second copy that could drift.

Oversells came from lag. A sale on one channel has to reach the others before the next shopper loads the page, so we moved sync from an hourly job to an event the moment stock changes.

The rollout added channels without adding chaos, because the hard decision, where truth lives, was made before the first listing went up.