API Development Services — REST, GraphQL & beyond.

API development is the process of designing, building, documenting, securing, and maintaining an Application Programming Interface — the set of rules that define how two systems exchange data. APIs power every modern application: a mobile app calls an API to fetch user data; a web dashboard calls one to display orders; a partner integration calls one to sync inventory. Every consumer of an API is a client depending on a contract — and that contract is what API development defines and enforces.

A complete engagement covers six phases: requirements and consumer mapping, contract design (OpenAPI spec), implementation, security hardening, documentation, and production monitoring. Most teams do only the middle two phases and skip the rest — which is why APIs ship without rate limiting, break partners without warning, and fail silently in production.

Choose REST for public APIs, mobile backends, and any API consumed by external developers. REST maps naturally to CRUD operations on resources, HTTP caching works with GET requests, and every developer already understands the pattern — it is the lowest adoption barrier.

Choose GraphQL when different client types need different data shapes from the same API. A mobile app needs five fields from a user object; a web dashboard needs twenty-two. REST returns all twenty-two in both cases (over-fetching) or needs a separate endpoint. GraphQL lets each client request exactly the fields it needs — at the cost of weaker HTTP caching and the need for query-complexity limits and DataLoader batching to avoid N+1 queries.

Choose gRPC for internal service-to-service communication in microservices. Protocol Buffers produce binary messages 5–10× smaller than equivalent JSON, and HTTP/2 multiplexing handles concurrent requests without head-of-line blocking. Not suitable for browser-facing APIs without a REST gateway.

Most production systems use all three: REST for public and partner APIs, GraphQL for the primary frontend API, and gRPC for internal microservice communication.

URL versioning (/v1/users, /v2/users) is the most explicit and developer-friendly — the version is visible in every request log, URL, and error report. Breaking changes go into a new version; old versions stay live until sunset. This is the right default for most APIs, with a minimum 6-month deprecation notice.

Header versioning (API-Version: 2026-01-01) keeps URLs clean and uses date-based versions — Stripe's approach. More expressive for fast-evolving APIs, but harder to debug because the version is invisible in the URL.

GraphQL schema evolution avoids versions entirely by deprecating individual fields with an @deprecated directive rather than creating a new endpoint. Fields stay available until all clients stop using them, which requires usage analytics to verify.

An idempotent operation produces the same result when executed multiple times. GET requests are naturally idempotent. POST requests are not — calling POST /orders twice creates two orders.

Network failures cause clients to retry requests without knowing whether the first attempt succeeded. A retry on a non-idempotent endpoint creates a duplicate: two charges, two orders, two emails. The solution is an idempotency key — a unique identifier the client sends in a header (X-Idempotency-Key: ord_7f3k9x). The server stores the key and result; on a retry with the same key, it returns the stored result without re-executing. We implement this on all write endpoints using Redis with a 24-hour TTL.

Good API documentation answers five questions without a support ticket: how to authenticate, what endpoints exist, what request body is required, what response to expect, and what to do when an error occurs. Interactive documentation — Swagger UI or Redoc rendered from an OpenAPI 3.0 spec — lets developers try endpoints directly in the browser with their actual API key. This is the minimum standard for any external or partner-facing API.

Complete docs include an authentication guide, code samples in JavaScript, Python, PHP, and cURL for every endpoint, an error-code reference, a changelog with breaking-change notices, and a migration guide per version. Teams that publish complete documentation receive far fewer integration support requests — the documentation is the support, not a substitute for it.