FastAPI is the preferred framework for building Python-based backend services, combining high performance with excellent developer ergonomics. Gary uses FastAPI for REST API development, real-time streaming endpoints, and AI agent service layers that require both speed and reliability.

Async patterns in FastAPI unlock high-throughput request handling, which is particularly important for AI-powered endpoints where inference calls may have variable latency. Proper async design ensures that slow AI operations do not block other requests, maintaining responsive service behavior under load.

Pydantic validation provides type-safe request and response handling that catches data issues at the API boundary. Combined with automatic OpenAPI documentation generation, this produces APIs that are self-documenting, easy to integrate with, and resistant to malformed input. Every API is designed with proper error responses, authentication, and rate limiting from the outset.