Articles on: Pareto - Order Limit Quantity

Checkout Timer & Inventory Lock

Reserve stock for a shopper while they check out, so limited-inventory drops never oversell.


How it works


During a limited campaign, many shoppers can reach checkout at the same time. Shopify only deducts inventory when an order is placed, so several shoppers can buy the last unit at once, which causes oversell and manual cancellations.


Checkout Timer & Inventory Lock fixes this by reserving a unit for a shopper when they add the item to cart or begin checkout, and showing a countdown. If they complete payment in time, the sale goes through. If the timer runs out, the item is removed from their cart and the unit is released for someone else, much like holding a seat when booking tickets.


The app keeps its own reservation counter and does not change your Shopify inventory levels. Shopify inventory stays the source of truth for fulfilment, and the "Only X left" counter continues to follow Shopify stock.


Select-type screen in Pareto admin, with a red arrow pointing to the Checkout Timer & Inventory Lock template



How to set it up

In the Pareto admin, create a new timer campaign. The form has two tabs: Timer settings and Message settings.


  1. Timer settings
  • Campaign name
  • Apply limit to: choose which products the reservation covers: All products, Specific products, Specific product variants, Specific collections, or Group of products.
  • Timer trigger: choose when the reservation starts: Customer adds to cart or Customer begins checkout (Shopify plus only)
  • Reservation duration: how long (in minutes) the unit is held.
  • Apply to markets, Target customer, and Schedule: the same options as your other Order Limit campaigns.


Create Checkout Timer & Inventory Lock screen, Limit settings tab showing Timer trigger, Reservation duration, and a cart preview with the item reserved



  1. Message settings
  • Timer running text and colors: the message on the countdown bar (default: "Your item is reserved for {{timer}}"), plus the bar background and text colors.
  • Expired notification:
    • Popup: hows the product with an "Add to cart again" button; you set the title, message, button labels, and colors.
    • Toast: shows a short message with a link back to the product page; you set the message, link text, and colors.
  • No-slot message and checkout-blocked message: the text shown when no unit is available.


Message settings tab of the campaign, showing Timer bar, Sold-out message, and Expired notification settings alongside a cart preview



Click Save, then turn the campaign on with the status toggle. The admin is available in English, Deutsch, Français, Español, Português (Brasil), and Chinese (Simplified and Traditional).


What customers see

  • Reservation starts: a countdown timer bar appears with your text and colors while the unit is held.
  • No unit available: the shopper sees "This item is no longer available" and the item is not added.
  • Timer runs out: the item is removed from the cart and the shopper sees your popup or toast. From the popup they can try "Add to cart again" (which starts a fresh timer if a unit is free, or shows "Sold out" if not).
  • Item removed from cart, or order placed: the reservation is released immediately.
  • Refreshing the page or reopening the cart keeps the same reservation and resumes the countdown.


Customer-facing cart with a countdown bar reading 'Your item is reserved for 2:26' below the product

Updated on: 08/07/2026

Was this article helpful?

Share your feedback

Cancel

Thank you!