Real-Time vs Scheduled Inventory Sync: Why the Gap Matters
Two sync tools can both claim to 'keep stock aligned' and be worlds apart. The difference is the window they leave open — and that window is where oversells live.
Updated July 19, 2026
Two inventory sync tools can both promise to 'keep your stock aligned' and behave completely differently in the one moment that matters: right after a sale. The difference is whether they sync in real time or on a schedule — and it decides how often you oversell.
How scheduled (polling) sync works
A scheduled tool wakes up on a timer — every 10, 15, or 30 minutes — asks each channel 'what's changed?', and copies the differences across. Between runs, it's blind. Everything that sells in that gap is unsynced, and every other channel keeps offering stock that may already be gone.
How real-time (webhook) sync works
A real-time tool doesn't wait. It subscribes to each channel's native webhooks, so the channel actively tells it the instant an order, refund, or stock change happens. The tool then pushes the new quantity to every other channel in seconds. There's no timer and no blind window to speak of.
Polling asks 'anything changed?' on a schedule. Webhooks say 'this just changed' the moment it does. That's the whole difference — and it's the difference between a several-minute oversell window and a several-second one.
A worked example
Say you have one unit of a popular item on Shopify and Amazon, and your tool polls every 15 minutes. A buyer takes it on Amazon at 2:03. Your next poll isn't until 2:15. For twelve minutes, Shopify still shows it as available — and if a second buyer checks out in that window, you've oversold, and you're cancelling an order that dents your account health.
With real-time sync, the Amazon sale at 2:03 fires a webhook, and Shopify drops to zero within seconds — usually around three. The second buyer never sees it as available. Same catalog, same traffic; the only variable is the size of the window.
When is scheduled sync 'good enough'?
Rarely, and only when the stakes are low: a handful of orders a week, deep stock on everything, and no marketplace that punishes cancellations. The instant you run promotions, sell thin stock, or list on Amazon, eBay, or Walmart, the polling window turns into cancellations.
How to evaluate a sync tool
- Ask how it detects a sale — 'webhooks' or 'real-time' is the answer you want; 'every X minutes' tells you the oversell window.
- Check both directions. Some tools push out fast but pull in on a timer. You want real-time both ways.
- Confirm it maps SKUs properly, so the right listings actually update.
- Look for a log and alerts, so you can trust and verify what it's doing.
Syncstocky is real-time-first: it subscribes to native webhooks the moment you connect a channel and propagates changes in seconds, both directions, with SKU mapping, a full Sync Log, and low-stock alerts. Shopify, Amazon, and eBay are live today.
Frequently asked questions
What does real-time inventory sync actually mean?
It means the sync reacts to a sale or stock change the instant it happens — via the channel's native webhooks — and updates your other channels within seconds, rather than checking for changes on a fixed schedule.
How big is the oversell window with scheduled sync?
Roughly equal to the polling interval. A tool that syncs every 15 minutes can leave stock overstated for up to 15 minutes after a sale — long enough to oversell on a busy item.
Is real-time sync always better?
For preventing oversells, yes — a smaller window is strictly safer. Scheduled sync is only 'good enough' at very low volume with deep stock and no cancellation-sensitive marketplaces in the mix.
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