| name | fastapi-dev |
| description | Guidelines and architecture patterns for FastAPI backend development, focusing on dependency injection, type safety, and clean routers. |
FastAPI Backend Guide
Follow this guide to build robust, framework-agnostic, and performant APIs.
Routing and Layer Separation
- Routers: Keep router code thin. Only validate request bodies/parameters and serialize responses. Delegate all business logic to service functions.
- Services: Write business logic in services that are database and framework-agnostic.
- Models: Use SQLAlchemy 2.0 async mapping for ORM models.
- Schemas: Always use Pydantic v2 schemas for request validation and response serialization. Never return raw database models directly.
Async Operations
- Use async router endpoints (
async def).
- Perform database interactions asynchronously using SQLAlchemy's
AsyncSession.
- Avoid mixing synchronous and asynchronous blocking calls (e.g. use non-blocking HTTP clients like
httpx instead of requests).
Dependency Injection
- Inject the database session and authentication details using FastAPI's dependency injection system (
Depends).
- Example:
from fastapi import APIRouter, Depends
from sqlalchemy.ext.asyncio import AsyncSession
from src.database import get_db
router = APIRouter()
@router.get("/items/{item_id}", response_model=ItemResponse)
async def read_item(item_id: int, db: AsyncSession = Depends(get_db)):
return await ItemService.get_item(db, item_id)
