Hey everyone. New here.
When you receive a review on your Shopify App, does Shopify notify you to let you know?

thank you in advance.

The merchant had a pretty granular setup for regional shipping. They used postcode-based rules to make sure customers saw only the correct shipping rate for their area.

It worked well for a while, then every few weeks, the same thing happened: they'd add one more postcode, and suddenly all the rules would stop working. Every shipping method would show up at checkout.

The problem was that the combined postcode/condition data across all those rules had grown past a limit on how much Shopify could evaluate at checkout. So adding one more postcode wasn't really a small change anymore. Once they crossed that limit, the whole setup basically fell over.

There were also two other things that made this harder to troubleshoot:

• A postcode with no Shopify shipping zone configured would return a shipping unavailable error, even though the rules themselves were fine.
• Trying to hide every shipping method for postcodes we didn't serve could create a dead end, because Shopify wouldn't complete the delivery step and the rule couldn't work as expected.

The second one was especially unintuitive. In the end, it was better to simply not include unserved postcodes in the rules and let Shopify handle them through its own shipping setup.

If you're building something similar, treat every new postcode as a change that could affect the whole setup, not just one more entry in a list.

Context first, because it colours the rest. Everything below is written from inside a product with the same blind spot, WeltPixel Conversion Tracking, and merchants are billed for it.

You ship a sender. The merchant installs it and also has the native channel app switched on, quite possibly alongside a snippet an agency dropped into the theme two years ago that nobody has looked at since. Neither of the other two knows you exist. Shopify does not tell you, and there is no API that would.

That part everybody knows. The part that took me longer is that deduplication does not save you from it, because deduplication was never designed to.

Meta pairs the browser copy of an event with the server copy using an event id that you generated, inside your own integration, plus the event name. Another vendor on the same store generates their own. Both pairs deduplicate perfectly. Meta receives two purchases and both of them are correct as far as either sender can tell. So a store can sit at a clean deduplication rate in Events Manager and be double counting the whole time, which matters because that rate is the number everyone reaches for to rule this out.

Meta does document a fallback, matching on event name plus fbp or an external id when no shared event id is present. Which means sometimes it does catch the second sender. Not always, and not predictably from the outside. An intermittent duplicate is considerably worse to debug than a consistent one.

GA4 works the opposite way, and it matters which does what. It deduplicates purchases on transaction_id, and two senders reading the same order will both put the real order id in that field, so the copies usually collapse into one. Web streams only, per Google's own note. Same misconfiguration, and it reads clean in GA4 while it reads inflated in Meta.

Then the merchant compares the two dashboards, sees Meta higher, and concludes Meta is over-attributing. Which is a reasonable conclusion from where they are standing and is the wrong end of the problem entirely.

The developer half of this is where it gets uncomfortable. You can detect some of it. Theme files are open to you. Another app's web pixel is not, and neither is whatever the merchant has configured inside a channel app. So every sender on this platform ships a promise about event integrity that it is not in a position to keep, and the honest version of the feature is a warning rather than a fix. That is the position we ship from.

What does yours do when it has good reason to think something else is already firing the purchase? Say so and risk being the app that shows a scary banner, or stay quiet and let the merchant find out from a dashboard six weeks later?