What in-memory database providers are available for testing?

Short answer: EF Core InMemory provider: Lightweight, fast, but doesn’t mimic relational database behavior exactly (no relational constraints, transactions). Other options: SQLite in-memory mode (better relational simulation). Use InMemory for unit tests; SQLite for more realistic integration testing.

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.