🔌 API Design Principles

APIs are promises. Once a consumer depends on an endpoint, changing it carelessly breaks trust and downstream systems. I treat every API as a product with real stakeholders, not just a technical artifact. Before writing a single route, I define the contract: what resources exist, what operations are allowed, what errors can be returned, and what guarantees the caller can rely on. This contract-first approach surfaces misunderstandings early, when the cost of change is low.

I follow RESTful conventions wherever they reduce friction — consistent resource naming, appropriate HTTP methods, standard status codes, and predictable error envelopes. For internal APIs or high-throughput scenarios I consider gRPC or GraphQL when the trade-offs justify it. Regardless of the protocol, every API needs versioning from day one. I prefer URI versioning (/v1/, /v2/) for its transparency and ease of routing, and I maintain older versions long enough for consumers to migrate without a crisis.

Pagination, filtering, and sorting are not afterthoughts — they are first-class requirements. An endpoint that returns unbounded collections will eventually cause a production incident. I design these capabilities into the initial contract and document them in the API spec, typically using OpenAPI. Generated documentation and mock servers let consumers develop against the API before the implementation is complete, accelerating parallel workstreams.

Security is embedded in API design from the start. Authentication (OAuth 2.0 / JWT), authorization at the resource level, rate limiting, and input validation are defaults, not add-ons. I also design APIs to be idempotent where possible, so that retries are safe and distributed systems can handle failures gracefully. An API built with these principles in place becomes an accelerator for product development rather than a recurring source of incidents.