In Denmark we have a “newish” national standard for public service architecture called rammearkitekturen. It’s an attempt to make IT easier and cheaper in a country with the most digitised public sector of the world where 98 muniplacities each have 300 different IT systems on average.

Part of it includes a transition to UUIDs, and the way we deal with them is slowly and in stages. Some systems, especially new ones are build to use them as the standard identification, but some of our systems are 50 years old, run on mainframes, tandem computers and what not, often with a range of APIs on top of them. Others were designed with local non-standard UUIDs that would work if the systems hadn’t been sold multiple times. And so on.

But the most basic way to get into them is by adding UUIDs for external use, while the systems continue using their own ID system internally. Then eventually replace internal IDs with the UUIDs when it becomes possible both technically and financially.

This isn’t the cleanest approach and it’ll likely take a decade or two to complete, but doing a Big Bang transition on an enterprise scale, well I wouldn’t recommend it.

As for standards, go with the newest international standard on UUIDs for you to part of the world. We follow EU.