What are foreign keys and primary keys?

Short answer: How to define them via annotations & Fluent API?

Explain a bit more

Primary Key (PK): Unique identifier of a record. Foreign Key (FK): A field that references a PK in another table. Data Annotations: [Key] public int Id { get; set; } [ForeignKey("Blog")] public int BlogId { get; set; } Fluent API: modelBuilder.Entity<Post>() .HasKey(p => p.Id); modelBuilder.Entity<Post>() .HasOne(p => p.Blog) .WithMany(b => b.Posts) .HasForeignKey(p => p.BlogId);

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.