ulid

I really like ULID for this problem (e.g: https://github.com/ahawker/ulid) - similar characteristics to UUID: same number of bytes, equivalent collision resistance, hard to guess, etc. - start with a date, is monotonic, and is lexicographically sortable: not only it has great locality but sorting is super easy and most code get it right by default. - can be created from an existing date or uuid, and exported to a uuid, so there is a migration path. - you get the creation date for free, which is always nice. As a bonus, you can now use the uuid as a base for dispatching, bracketing, sharding, etc.

As the author of a popular ULID implementation in python[1], the spec has no stewardship anymore. The specification repo[2] has plenty of open issues and no real guidance or communication beyond language implementation authors discussing corner cases and the gaps in the spec. The monotonic functionality is ambiguous (at best), doesn't consider distributed id generation, and is implemented differently per-language [3]. Functionally, UUIDv7 might be the _same_ but the hope would be for a more rigid specification for interoperability. [1]: https://github.com/ahawker/ulid [2]: https://github.com/ulid/spec [3]: https://github.com/ulid/spec/issues/11

Looks similar to ULID[0] (I am the author of a popular python implementation[1]). It appears to have a similar constraint that two ID's generated within the same timestamp (ms, ns) have no strong guarantee of ordering. That might not be a deal breaker depending on your use case but something to consider. * https://github.com/ulid/spec * https://github.com/ahawker/ulid