ULID: Universally Unique Lexicographically Sortable Identifier

> It is worth noting that the newest proposed standard for unique identifiers, UUID v7, aims to address the sortability and database performance issues of older UUID versions by adopting a similar time-ordered structure to ULID.

Yeah, I would go with UUID v7 at this point given that it's part of the UUID RFC https://datatracker.ietf.org/doc/html/rfc9562#name-uuid-vers...

Whenever ULID comes up, I need to remind that it has a sequential ID generation mode in its spec which is prone to conflicts on multi-threads, processes or hosts which kills the purpose of a "universal" identifier. If you need a sequential ID, just use an integer, preferably one that's autoincremented by the database.

It's best to stick to UUIDv7 because of such quirks of ULID.

Mentioned in the article's comments:

> Why not use UUID7?

> "ULID is much older than UUID v7 though and looks nicer"

For those unfamiliar, UUIDv7 has pretty much the same properties – sortable, has timestamp, etc.

ULID: 01ARZ3NDEKTSV4RRFFQ69G5FAV

UUIDv7: 019b04ff-09e3-7abe-907f-d67ef9384f4f

BTW, this doesn’t work well in S3 due to the timestamp being to the left of the randomness.

I have always been a bit hesitant to use UUIDs with timestamps as it can be a security issue if the IDs are public. For example getting the age of a user account just from the id. I will say, however, that I have not heard of any major incidents stemming from this.

I love the aesthetics. The cryptographic strength tradeoffs (against UUIDv7) seem rough for a lot of applications, though.

i keep a list of UUID info: https://github.com/swyxio/brain/blob/master/R%20-%20Dev%20No...

for those also learning

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Universally distinct would seem more correct than unique, at least mathematically speaking, unless there's only ever going to be just one of them.

Interesting article noting how ULIDs solve database index fragmentation caused when using UUIDv4. However, for extremely high-volume writes, ULIDs create "hot spots" at the current timestamp index location, potentially causing contention. The article notes that UUID v7 (newly standardized) adopts the same time-ordered approach, validating ULID's design.