Fastapi Templates

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

Implementation Patterns

Pattern 1: Complete FastAPI Application

# main.py
from fastapi import FastAPI, Depends
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager

@asynccontextmanager
async def lifespan(app: FastAPI):
    """Application lifespan events."""
    # Startup
    await database.connect()
    yield
    # Shutdown
    await database.disconnect()

app = FastAPI(
    title="API Template",
    version="1.0.0",
    lifespan=lifespan
)

# CORS middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Include routers
from app.api.v1.router import api_router
app.include_router(api_router, prefix="/api/v1")

Resources

• references/fastapi-architecture.md: Detailed architecture guide
• references/async-best-practices.md: Async/await patterns
• references/testing-strategies.md: Comprehensive testing guide

Best Practices

1. Async All The Way: Use async for database, external APIs
2. Dependency Injection: Leverage FastAPI's DI system
3. Repository Pattern: Separate data access from business logic
4. Service Layer: Keep business logic out of routes
5. Pydantic Schemas: Strong typing for request/response
6. Error Handling: Consistent error responses
7. Testing: Test all layers independently

Common Pitfalls

• Blocking Code in Async: Using synchronous database drivers
• No Service Layer: Business logic in route handlers
• Missing Type Hints: Loses FastAPI's benefits
• Ignoring Sessions: Not properly managing database sessions
• No Testing: Skipping integration tests
• Tight Coupling: Direct database access in routes