I used ULIDs for a time until i discovered snowflake ids. They are (“only”) 64 bits, but incorporate timestamps and randomness as well. They take up way less space than ULIDs for this purpose and offer acceptably rare collisions for things I’ve worked on.
The original snowflake id developed at twitter contains a sequence number so they should never collide unless you manage to overflow the sequence number in a single millisecond.
Also, you can store them as a BIGINT, which is awesome. So much smaller than even a binary-encoded UUID. IIRC the spec reserves the right to use the sign bit, so if you’re concerned, use BIGINT UNSIGNED (natively in MySQL, or via extension in Postgres).
I wish more people cared about the underlying tech of their storage layer – UUIDv4 as a string is basically the worst-case scenario for a PK, especially for MySQL / InnoDB.
