---
name: fastapi-templates
description: Create production-ready FastAPI projects with async patterns, dependency injection, and comprehensive error handling. Use when building new FastAPI applications or setting up backend API projects.
---
# FastAPI Project Templates
Production-ready FastAPI project structures with async patterns, dependency injection, middleware, and best practices for building high-performance APIs.
## When to Use This Skill
- Starting new FastAPI projects from scratch
- Implementing async REST APIs with Python
- Building high-performance web services and microservices
- Creating async applications with PostgreSQL, MongoDB
- Setting up API projects with proper structure and testing
## Core Concepts
### 1. Project Structure
**Recommended Layout:**
```
app/
├── api/ # API routes
│ ├── v1/
│ │ ├── endpoints/
│ │ │ ├── users.py
│ │ │ ├── auth.py
│ │ │ └── items.py
│ │ └── router.py
│ └── dependencies.py # Shared dependencies
├── core/ # Core configuration
│ ├── config.py
│ ├── security.py
│ └── database.py
├── models/ # Database models
│ ├── user.py
│ └── item.py
├── schemas/ # Pydantic schemas
│ ├── user.py
│ └── item.py
├── services/ # Business logic
│ ├── user_service.py
│ └── auth_service.py
├── repositories/ # Data access
│ ├── user_repository.py
│ └── item_repository.py
└── main.py # Application entry
```
### 2. Dependency Injection
FastAPI's built-in DI system using `Depends`:
- Database session management
- Authentication/authorization
- Shared business logic
- Configuration injection
### 3. Async Patterns
Proper async/await usage:
- Async route handlers
- Async database operations
- Async background tasks
- Async middleware
### 4. Dependencies
The packages the examples import:
```text
# requirements.txt
fastapi
uvicorn[standard]
pydantic-settings
sqlalchemy[asyncio]>=2.0 # DeclarativeBase; [asyncio] installs greenlet for the async engine
asyncpg # PostgreSQL driver: postgresql+asyncpg://...
PyJWT
pwdlib[argon2]
python-multipart # only for a login route that uses OAuth2PasswordRequestForm
# requirements-dev.txt
pytest
pytest-asyncio
httpx
aiosqlite # test database: sqlite+aiosqlite:///:memory:
```
## Detailed worked examples and patterns
Detailed sections (starting with `## Implementation Patterns`) live in `references/details.md`. Read that file when the navigation summary above is insufficient.
## Testing
```python
# tests/conftest.py
import pytest_asyncio
from httpx import ASGITransport, AsyncClient
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from sqlalchemy.orm import sessionmaker
from app.main import app
from app.core.database import get_db, Base
TEST_DATABASE_URL = "sqlite+aiosqlite:///:memory:"
# Async fixtures need pytest_asyncio.fixture in pytest-asyncio's default strict mode
@pytest_asyncio.fixture
async def db_session():
engine = create_async_engine(TEST_DATABASE_URL, echo=True)
async with engine.begin() as conn:
await conn.run_sync(Base.metadata.create_all)
AsyncSessionLocal = sessionmaker(
engine, class_=AsyncSession, expire_on_commit=False
)
async with AsyncSessionLocal() as session:
yield session
await engine.dispose()
@pytest_asyncio.fixture
async def client(db_session):
async def override_get_db():
yield db_session
app.dependency_overrides[get_db] = override_get_db
# httpx 0.28 removed AsyncClient(app=...); use an ASGI transport
transport = ASGITransport(app=app)
async with AsyncClient(transport=transport, base_url="http://test") as client:
yield client
app.dependency_overrides.clear()
# tests/test_users.py
import pytest
@pytest.mark.asyncio
async def test_create_user(client):
response = await client.post(
"/api/v1/users/",
json={
"email": "[email protected]",
"password": "testpass123",
"name": "Test User"
}
)
assert response.status_code == 201
data = response.json()
assert data["email"] == "[email protected]"
assert "id" in data
```