items["latte"]["ingredients"] = ["water", "milk", "sugar", ...]
He had individual flags for every item for every possible ingredient it could have or not have: items["latte"]["has_milk"] = true
items["latte"]["has_nutmeg"] = false
items["latte"]["has_cinnamon"] = false
items["latte"]["has_sugar"] = true
...
This technically worked and passed tests from his POV at an MVP level. But added a lot of complications when actually trying to build more features or when a new menu item had ingredients the founder hadn't thought to include in the schema beforehand.
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