api-and-interface-design

To design stable REST API contracts, apply version-safe additive changes, boundary-only validation, and consistent error semantics so observable behaviors remain predictable for long-lived consumer compatibility. Treat Hyrum’s Law as a constraint by intentionally exposing and deprecating behaviors.

The best way to handle API validation boundaries is to validate requests and external-service responses at system edges using Pydantic and FastAPI, ensuring internal code can fully trust typed inputs. This prevents unvalidated data from propagating through your system logic.

Hyrum’s Law affects interface design by treating observable behaviors like error timing, ordering, and responses as implicit commitments that constrain public API evolution. You must design for intentional exposure and deprecation to safely evolve interfaces without breaking consumer implementations.

Yes, you can use TypeScript discriminated unions and branded nominal ID types to enforce type-system correctness and prevent category errors in frontend-backend interface contracts. These patterns create immutable value objects that make APIs hard to misuse at compile time.

To implement consistent PATCH partial updates and idempotent delete patterns in REST, define clear contract-first typing rules for partial resource modifications and ensure predictable client expectations across pagination and filtering operations. This maintains semantic consistency across your API surface.

You need contract-first typing for Python module boundaries when specifying protocol-style interfaces before implementation to ensure safe evolution of existing public interfaces between internal modules. This approach reduces ambiguity and prevents breaking changes when modules are updated independently.