What are concurrency tokens / row versioning?

Short answer: Properties marked with [Timestamp] or configured as concurrency tokens. Stored in the database as rowversion/timestamp type or other markers. EF Core checks these tokens during updates/deletes to detect concurrent changes.

Real-world example (ShopNest)

ShopNest’s order service uses EF Core to save an Order and its line items in one SaveChangesAsync() call inside a transaction.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.