Explain the concept of Schema-First vs Code-First development.

Schema-First designs the SDL as a string, then binds resolvers. Code-First writes classes/functions, which automatically generate the SDL.

Schema-First (e.g., Apollo Server) enforces contract-driven development but often leads to typing mismatches between the SDL and TypeScript resolvers. Code-First (e.g., TypeGraphQL, NestJS) uses decorators or strongly-typed objects to generate the schema, ensuring a single source of truth and perfect type safety.