Several listings share one shelf of stock. Shopify tracks each variant separately so one sells out while the others still show stock. PoolKeeper gives those variants one shared pool. Set the quantity and how much each variant uses; every sale or restock resets the others to match. Multipliers handle packs and weight. Compare-and-set writes never overwrite a sale in flight. Reconcile and buffer keep stock accurate; the activity log records every change.

• Compare-and-set writes: never overwrites a sale in flight, so no overselling
• Multipliers for packs and weight: 6-packs, 0.5 kg bags, metres of fabric
• Full audit log of every sale, restock and correction, with before and after
• Hourly reconcile and a stock buffer keep every listing accurate