1
Key Concepts
There are two common approaches to multi-marketplace inventory: batch sync (updates pushed on a schedule, e.g. every 30-60 minutes) and true real-time sync (updates pushed the instant a sale is confirmed). Batch sync feels "good enough" until a high-velocity SKU sells out on one platform during the gap between syncs — at which point it's still shown as available on every other platform, creating an oversold order that has to be manually cancelled.
2
Best Practices
For your top 10-20% of SKUs by sales velocity, insist on true real-time sync — the gap window is where overselling actually happens, and it happens disproportionately on your best sellers. For slower-moving SKUs, batch sync every 15-30 minutes is usually sufficient and less resource-intensive. Always maintain a small safety buffer (even 1-2 units) on your fastest SKUs specifically to absorb any sync delay, however small.
3
Implementation
Check whether your current setup (if any) syncs inventory in real time or on a batch schedule — many sellers assume real-time sync when they're actually on a 30-60 minute batch cycle. An OMS connected directly to each marketplace's API via webhooks (not scheduled polling) achieves true real-time sync, decrementing stock across every connected platform the moment an order is confirmed anywhere.
Pro Tip
Overselling almost always happens on your fastest-moving SKUs during high-traffic periods — that's exactly when sync delays matter most and when the cost of a cancelled order (to your seller rating) is highest.
Key Takeaways
- Batch sync creates a real gap window where overselling can happen
- Prioritize true real-time sync for your top 10-20% of SKUs by velocity
- Keep a small safety buffer on fastest-moving SKUs to absorb sync delays
- Check whether your current sync is truly real-time or just frequent batch updates
- Webhook-based sync (not scheduled polling) is what achieves genuine real-time updates
