If you have built a Shopify integration before, you have hit this wall. Your warehouse system shows 50 units. Shopify shows 45. An order comes in for 10 units. Now you have a problem you did not plan for. This is eventual consistency at work. And it is one of the most common sources of production bugs in Shopify-connected systems. This post walks through why it happens and exactly how to handle it. What Eventual Consistency Actually Means Eventual consistency means all systems will reflect the same data state eventually, but not at the same instant. It sits at the opposite end of the spectrum from strong consistency, where every read returns the latest write. Strong consistency requires locking and synchronous coordination. That works fine on a single database. It does not scale to distributed commerce infrastructure serving millions of merchants. Shopify prioritizes availability and performance over strict consistency. That is the right call for a platform at its scale.…