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Notes from the database side of identifiers: when a random v4 is fine, when a time-ordered v7 saves your indexes, how a GUID differs from a UUID, and the one-liners that generate them in the languages you already use.
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UUID v4 vs v7: which one belongs in your primary keyRandom v4 or time-ordered v7? What each does to a B-tree index, what v7 reveals about your rows, and a safe way to switch.Reading time: 7 min
UUID vs GUID: the same 128 bits with different habitsSame standard, different habits: braces, upper case, the old Microsoft variant, and the byte swap that breaks GUIDs on their way out of .NET.Reading time: 6 min
How to generate a UUID in PostgreSQL, JavaScript, Python, Java and C#The v4 one-liner, the v7 option and the name-based call in five languages, plus what MySQL and SQL Server do differently.Reading time: 6 min