Inventory Write-Back: How It Works and Why It Matters

Inventory write-back is one of the most critical features for multi-store merchants. Without it, you'd oversell — a customer buys the last unit on your server store, but client stores still show it as in stock.

The problem write-back solves

Imagine you run a wholesale store (server) and two retail stores (clients). A wholesale order comes in for 10 units of SKU-1042. Without write-back, your retail stores still show 10 units available. With write-back, the inventory update propagates to all clients within milliseconds.

How it works technically

1. A sale occurs on the server store
2. Shopify fires an orders/paid webhook to MultiStore Sync
3. The app reads the line items and their SKUs
4. For each SKU, it calls the Inventory API on every connected client store
5. Inventory levels are decremented to match

Multi-location support

MultiStore Sync handles multi-location inventory correctly. If your client store has multiple locations, the write-back targets the primary location by default. You can configure per-store location preferences in Settings.

What about partial fulfillment?

Write-back fires on orders/paid, not on fulfillment. This is intentional — you want inventory reserved as soon as payment is confirmed, not when the item ships.