Goodbye integers, hello UUIDv7

For the curious:

* UUIDv4 are 128 bits long, 122 bits of which are random, with 6 bits used for the version. Traditionally displayed as 32 hex characters with 4 dashes, so 36 alphanumeric characters, and compatible with anything that expects a UUID.

* UUIDv7 are 128 bits long, 48 bits encode a unix timestamp with millisecond precision, 6 bits are for the version, and 74 bits are random. You're expected to display them the same as other UUIDs, and should be compatible with basically anything that expects a UUID. (Would be a very odd system that parses a UUID and throws an error because it doesn't recognise v7, but I guess it could happen, in theory?)

* ULIDs (https://github.com/ulid/spec) are 128 bits long, 48 bits encode a unix timestamp with millisecond precision, 80 bits are random. You're expected to display them in Crockford's base32, so 26 alphanumeric characters. Compatible with almost everything that expects a UUID (since they're the right length). Spec has some dumb quirks if followed literally but thankfully they mostly don't hurt things.

* KSUIDs (https://github.com/segmentio/ksuid) are 160 bits long, 32 bits encode a timestamp with second precision and a custom epoch of May 13th, 2014, and 128 bits are random. You're expected to display them in base62, so 27 alphanumeric characters. Since they're a different length, they're not compatible with UUIDs.

I quite like KSUIDs; I think base62 is a smart choice. And while the timestamp portion is a trickier question, KSUIDs use 32 bits which, with second precision (more than good enough), means they won't overflow for well over a century. Whereas UUIDv7s use 48 bits, so even with millisecond precision (not needed) they won't overflow for something like 8000 years. We can argue whether 100 years is future proof enough (I'd argue it is), but 8000 years is just silly. Nobody will ever generate a compliant UUIDv7 with any of the first several bits aren't 0. The only downside to KSUIDs is the length isn't UUID compatible (and arguably, that they don't devote 6 bits to a compliant UUID version).

Still feels like there's room for improvement, but for now I think I'd always pick UUIDv7 over UUIDv4 unless there's an very specific reason not to. Which would be, mostly, if there's a concern over potentially leaking the time the UUID was generated. Although if you weren't worrying about leaking an integer sequence ID, you likely won't care here either.

> values generated are practically sequential

These statements aren’t strict enough to be relied on. Maybe you have engineered the hell out of your distributed clock scheme, and your IDs actually are completely monotonic, which is great. But you probably haven’t done that, which means conflicts will surely happen and you must handle them gracefully.

As Lazare points out in this thread they're basically the same thing, except with ULIDs you get those 6 extra bits of randomness back that UUIDs have to use for metadata.

Or better yet, only decorate one after it has been clicked by the user, that way when it appears again elsewhere, it stands out. If you make each one pretty you'll have made all of them ugly when viewed together.