API

APIs are the connective tissue of modern products. This guide distills proven practices for API design, security, observability, and reliability—covering the most frequent questions and edge cases teams face in production. Examples use FastAPI and Pydantic v2, but the principles generalize to any stack.

New to APIs? This guide explains core concepts in clear language, then walks you through building a small FastAPI service with essential security and testing tips. When you’re ready for advanced patterns, read the companion: Designing Secure and Scalable APIs — A Comprehensive Guide.