Preorder limits during high-volume launches
Use this guide if you're planning a preorder launch you expect to draw a large burst of orders in a short window, for example an announced drop time, a limited-run collectible, or a highly anticipated restock. It explains why a STOQ preorder quantity limit can be crossed during that kind of surge, and how to set the offer up so it can't happen.
A STOQ preorder quantity limit enforces its cap by watching orders as they come in, not by blocking them at checkout. During a normal trickle of orders that's invisible. During a synchronized burst of hundreds of orders in a few minutes, orders can keep clearing for a short time after the limit is technically reached, because each one has to be counted before the offer turns itself off. The result is more units sold than the limit allowed.
How the quantity limit enforces its cap
A STOQ preorder quantity limit only works on offers using the Show "Preorder" when product is out of stock inventory setting (see Configure inventory settings). Under that setting, STOQ tracks each variant's own preorder count and turns off Continue selling when out of stock once the count reaches the limit. That means:
- Shopify accepts the order first.
- STOQ then recounts the variant's total preorders and checks it against the limit.
- If the limit is now reached, STOQ turns off Continue selling for that variant so the next order is blocked.
Each of these steps takes a little time. For ordinary order volume, that delay is too short to matter. For a launch where hundreds of customers are all trying to buy the same variant within minutes of each other, a wave of orders can be accepted before the earlier ones have finished being counted, so the cap ends up crossed rather than held exactly.
Use Shopify's own inventory as the cap instead
For a launch you expect to move fast, the more reliable setup is to switch the offer's Inventory setting to Show "Preorder" for in-stock products (see Configure inventory settings). On that setting, availability is governed by your Shopify inventory count directly, and Shopify's own checkout enforces it — there's no separate STOQ count that needs to catch up, so it can't be outrun by order volume.
Switching to Show "Preorder" for in-stock products only works with the Specific products type, resets inventory deduction to At checkout, and needs an actual Shopify inventory quantity to count down from — it isn't a drop-in swap for every out-of-stock offer. If your products are already at zero stock and you can set a real inventory number to sell against (your intended cap), this is the setup that can't oversell. See Configure inventory settings for the full comparison.
If you're staying on a STOQ-tracked quantity limit
Some launches can't move to the in-stock setting, for example genuine backorders with no stock to allocate. If you're staying on a STOQ preorder quantity limit for a launch you expect to surge:
- Set the limit a bit below the true number you're willing to sell, so there's headroom if a burst of orders clears in the same few minutes the cap is reached.
- Avoid publicizing an exact go-live second to a large audience where possible; a launch that ramps up over a minute or two gives the count time to keep up, where an instant, synchronized rush doesn't.
FAQ
Why did my preorder oversell even though I had a quantity limit set?
The quantity limit counts orders after Shopify accepts them, then turns off further selling. In a normal launch that's fast enough to matter; in a launch that draws a large burst of simultaneous orders, more orders can be accepted than the count has had time to catch up with. See How the quantity limit enforces its cap above.
What's the safest setup for a launch I expect to sell out in minutes?
Switch the offer's Inventory setting to Show "Preorder" for in-stock products, so Shopify's own inventory count and checkout enforce the cap directly. See Use Shopify's own inventory as the cap instead above.
Can I use both the in-stock setting and a STOQ quantity limit together?
No. STOQ quantity limits only apply to offers using the out-of-stock inventory setting. An in-stock offer is capped by its Shopify inventory count instead.
