A short guide to organizing FastAPI apps beyond a single main.py file.

FastAPI makes it easy to start with a single main.py file. That is great for demos, prototypes, and small APIs.

But once your application grows, one file can quickly turn into a mix of routes, database logic, security helpers, settings, and business rules. A clear project structure helps keep the app easier to understand, test, and extend.

Here is a practical FastAPI structure for growing backend applications:

. ├── app/ │ ├── api/ │ │ └── v1/ │ │ ├── endpoints/ │ │ └── router.py │ ├── core/ │ ├── crud/ │ ├── db/ │ ├── models/ │ ├── services/ │ └── main.py ├── alembic/ ├── docs/ ├── scripts/ ├── tests/ ├── .env.example ├── alembic.ini ├── docker-compose.yaml ├── Dockerfile ├── pyproject.toml └── README.md

Enter fullscreen mode

Exit fullscreen mode

app/main.py

This is the application entry point.

Use it to create the FastAPI() app, register routers, configure lifespan events, add middleware, and expose basic endpoints like…