ULID: Universally Unique Lexicographically Sortable Identifier

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.

Under what circumstances is it prone to conflicts? On separate threads/hosts/processes, id's created within the same millisecond would be differentiated by the 80 bits of randomness (more than UUID v7).