The Shop on the Corner: How I Learned System Design Without Building Amazon

Nephew asks his uncle — 10 years deep into building large-scale systems — to explain "system design," and all the scary jargon that comes with it. Uncle refuses to start with the jargon. Instead: "Forget servers and databases for a minute. Just imagine you're running a small shop." What follows is a thought experiment, built one problem at a time — no cloud bills, no fancy stack, just a counter, a storeroom, and a lot of common sense.

Part 1: The Counter — Your First "API"

Here's the shape of what you just described, whether you realized it or not:

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