What type of identifier have you used — UID or numeric ID — in your project?

Choosing between UID (such as UUID) and a numeric ID depends on project requirements.

A numeric ID is usually used as an auto-increment field in a database. It is simple, compact, and convenient for indexing, but can be predictable and not unique outside a single database.

A UID (e.g., UUID) is a 128-bit identifier that guarantees global uniqueness. It is useful in distributed systems where objects are created on different servers and collisions must be avoided.

In my projects, I used numeric IDs for internal tables and relationships, and UUIDs for public APIs and integrations to ensure security and uniqueness.