FastAPI Patterns

Modern FastAPI (0.100+) with Pydantic v2, async-first, and typed throughout.

When to Activate

• Structuring a FastAPI app with routers and layered architecture
• Designing dependency injection chains with Depends
• Defining Pydantic v2 request/response schemas
• Handling errors, custom exception handlers, or middleware
• Adding authentication (OAuth2, JWT, API keys)
• Writing background tasks or startup/shutdown logic
• Testing FastAPI routes with TestClient or async httpx

Project Structure