For a long time, if you wanted a primary key that was both unique and chronological, you reached for ULID . It was the perfect "indie" solution to the randomness of UUID v4. It gave us fast database inserts and clean, copy-pasteable URLs. But the world of standards moves fast. In 2024, the IETF officially published RFC 9562, which introduced UUID v7 . It does almost exactly what ULID does: it embeds a timestamp into the first part of the ID. If you are starting a new Rails 8 app today, you might be wondering: "Is ULID still relevant, or should I switch to the 'official' UUID v7?" I’ve looked at both, and while they serve the same purpose, the choice usually comes down to a battle between Native Performance and Developer Experience (Readability) . Here is the breakdown.…