UUID

Why instead of a numeric ID

• Does not reveal the number of records in a table (/users/1 vs /users/550e8400-…)
• Can be generated on the client or in a distributed system without a DB round-trip
• No conflicts when merging data from multiple databases

Versions

• UUID v4 — fully random. Most common
• UUID v7 — includes a timestamp, so it sorts chronologically. Better for DB primary keys (less index fragmentation)

Drawback

UUID v4 as an InnoDB primary key causes B-Tree index fragmentation due to random insert order. UUID v7 or ULID solve this problem.