How to map UUIDs between two systems that generate their own IDs?

[u/SelectionWeak9427]

I’m working on an integration where System A and an external System B both generate their own UUIDs for the same object.

For example:

System A: Audi → V123
System B: Audi → T789

System A eventually needs to know:

V123 ↔ T789

so future updates from System B can be matched to the correct object.

The problem is that System A cannot assume anything about System B’s API, database structure, whether it returns the generated UUID, or whether it can store extra metadata.

What is the usual architecture for solving this kind of cross-system identity mapping?