A discount engine built to hold up on Black Friday, not just on a Tuesday in March
Most discount apps work fine on ordinary traffic. Peak traffic is where the shortcuts show. This page covers why discount apps fail during BFCM, a short playbook for running discounts through peak, and exactly what Stackable commits to, in verifiable terms, not an uptime number nobody can check.
Install freePublic reviews of discount apps describe the same failure mode every BFCM season:
“The app is literally broken for Black Friday. It worked fine all year and then broke out of nowhere during our biggest traffic day, costing us thousands before we caught it.”
Two shortcuts explain most of it
Two shortcuts explain most of the pattern:
Client-side price hacks
Some apps calculate the discount in the browser and rewrite the displayed price with JavaScript. It looks right in the cart, but the actual checkout total is computed separately, by Shopify's checkout, not the app. Under peak load, or with a slow connection, or with an ad-blocker, that JavaScript can fail silently while the visual price stays discounted. The customer sees one number; checkout charges another.
Draft-order checkouts
Other apps route the cart through a draft order to apply custom pricing, a workaround that predates Shopify Functions. Draft orders sit outside the normal checkout flow, which breaks native discount codes and order analytics, and adds another moving part that can fail exactly when traffic spikes.
A short BFCM checklist
Schedule your campaigns ahead of the rush
Set exact start and end dates before BFCM week, so nothing depends on someone manually flipping a campaign live while checking traffic dashboards at the same time.
Run a sample cart through the simulator first
Before a campaign goes live, test it against a sample cart and confirm the combined total is exactly what you expect, the same calculation checkout will run.
Know you can pause instantly if something looks wrong
If a campaign is behaving unexpectedly once it's live, pausing it takes one click and applies storefront-wide, not just on new page loads.
Verifiable specifics, not an uptime number
We'd rather commit to things you can check on your own store than publish a number we can't back yet.
Common questions
What makes Stackable different at BFCM traffic levels specifically?
The discount calculation runs inside the same Shopify Function infrastructure regardless of traffic volume, there is no separate "peak mode" or client-side fallback that behaves differently under load. The same server-side calculation runs whether it is a normal Tuesday or your highest-traffic hour of the year.
Can I schedule a campaign to start exactly at midnight on Black Friday?
Yes. Set the start and end date and time when you create the campaign, and it activates and deactivates automatically on schedule without anyone needing to be online at that moment.
If I need to stop a campaign mid-BFCM, how fast does that take effect?
Pausing a live campaign takes one click in the admin and propagates storefront-wide within 60 seconds.
Do you publish an uptime number?
Not yet, and we would rather not publish a number we can't back with a track record. What we can commit to today is architectural: server-side computation, identical totals across cart and every checkout surface, and a fast, verifiable pause.
Run your BFCM discounts on a server-side engine
Schedule ahead, test with the simulator, and pause in one click if you need to, all season long.
Free plan available. No card required.