alt Hacker News> Your notion that you can avoid sharing internal ids is technically true, but that didn’t mean it’s a good idea. You’re trying force a philosophical viewpoint and disregarding practical concerns, many of which people have already pointed out.
What some call "philosophical viewpoint" I call "essential complexity" :)
> But to answer your question, yes, your customer will probably have some notion of a transaction id. This is why everyone gives you invoice numbers or order numbers.
We are in agreement here: externally visible identifiers are needed for many reasons (mostly technical). The discussion is not about that though but about what information should be included in these identifiers.
> This is why everyone gives you invoice numbers or order numbers.
And there are good reasons why invoice or order numbers are not randomly generated strings but contain information about the invoices and orders they identify.
My claim is that externally visible identifiers should possess a few characteristics:
* should be based on the data they identify (not detached from it)
* should be easy to remember (and that means they should be as short as possible, they should be easy to construct by a human from the data itself - so they cannot be hashes of data)
* should be versioned (ie. they should contain information somehow identifying the actual algorithm used to construct them)
* should be easy to index by database engines (that is highly db implementation dependent unfortunately)
* can be meaningfully sortable (that is not strictly a requirement but nice to have)
Coming up with an identifier having these characteristics is not trivial but is going to pay off in the long run (ie. is essential complexity).
Much of this is not essential complexity, but accidental complexity.
* Based on the data they identify - This is a minefield of accidental complexity. Data changes and needs to be redacted for GDPR and other data laws. What do you do when someone demands you delete all personally identifiable data but you’ve burned it into invoice ids that you need to retain for other legal reasons? This is also begging for collisions and very much at odds with making IDs short.
* easy to remember - This is a nice to have. Short is convenient for sharing on the phone. Memorable didn’t matter much. I don’t remember any invoice number I’ve ever received.
* versioned - Versioning is only interesting because you’re trying to derive from real data. Again, accidental complexity.
* easy to index - Sure.
* sortable - Nice to have at best.