I'm not talking about cryptographic keys, I'm talking about unique keys. Like a UUID or a serial number. A barcode is not often used as the sole storage medium

I'm not talking about cryptographic keys, I'm talking about unique keys. Like a UUID or a serial number. A barcode is not often used as the sole storage medium in an application. Typically it's used in conjunction with a piece of software that can connect to a database. In a manufacturing setting this could be a piece of shop floor control software. In that setting the barcode doesn't encode any information that could change in the database. It is instead used to encode a machine-readable identifier for the material that it is labeling.