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    I was a little surprised they mentioned KSUID but not Snowflake or Flake which are how a lot of teams learned about k-ordered ids originally. Perhaps I’m just old. I re-implemented flake in Haskell for fun awhile back.

    Doesn’t talk about the motivations for k-ordering or sortability as it pertains to database indexes either. UUIDv4 has a habit of spraying btree indexes in unpleasant ways. This summarizes the motivations for Flake’s design: http://yellerapp.com/posts/2015-02-09-flake-ids.html

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      there is also ULID [1]

      a comparasing with KSUID [2]

      [1] https://github.com/ulid/spec

      [2]https://github.com/segmentio/ksuid/issues/8

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        A long time ago I found a site for the UUID Preservation Society, encouraging all programmers to limit their use of UUIDs lest they run out. This seems like something they would get behind.

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          error processing BAE7DF4-DDF-3RG-5TY3E3RF456AS10: nil

          So you are blaming poor logging or error handling on the type of an identifier used? Sorry but this point is nonsensical enough that I stopped reading right at the beginning of an article.

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            Are there any hierarchical UUIDs out there? That is, given two UUIDs, I can quickly check if they might be related, without looking at a database?

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              Depends on what you mean by “hierarchical”, but likely no. The closest you could come is a UUIDv1 which contains the MAC of the generating node; so long as all your UUIDs are v1 and generated by the same node, they’d have that in common.

              For other versions, not really. A v4 UUID is random. And v3 or v5 UUID is just a UUID of a hash of a namespace+name combination (the difference being the hash algorithm – MD5 for v3, SHA-1 for v5), where the desirable property is that the same combination of namespace+name produces the same output every time. For example, no matter what language or system you use, as long as it’s RFC4122-compliant, would give the output UUIDv3 9073926b-929f-31c2-abc9-fad77ae3e8eb for the domain name example.com. But v3 and v5 UUIDs don’t have a way to recover the input namespace or name from the output UUID.