What is the difference between schema-first and code-first GraphQL approaches?

In the schema-first approach, you write SDL (schema definition language) first, then implement resolvers that match the schema. This makes the schema the source of truth and is great for API-first design where the contract is agreed upon before implementation. Tools like Apollo Server and graphql-tools support this. In the code-first approach, you write resolver code and the schema is generated automatically from it. Libraries like TypeGraphQL (TypeScript decorators) and Strawberry (Python) use this approach. Code-first avoids schema/resolver drift since the schema is derived from the code, but schema-first is often preferred for multi-team APIs where the contract needs to be explicitly designed.