How to Build a Python FastAPI Backend

Async-first, typed, production-ready - the FastAPI setup that handles real traffic.

FastAPI is the fastest-growing Python web framework for good reasons: automatic OpenAPI docs Pydantic validation native async and dependency injection built in. This guide covers the project structure async SQLAlchemy integration and security patterns that make a FastAPI backend production-ready.

No fluff. Production-grade answers from engineers who build this every day.

Why FastAPI Over Django REST Framework?

Django REST Framework is excellent for teams that need the full Django ecosystem: ORM admin panel authentication batteries included. FastAPI wins on performance type safety and developer experience for API-first applications. The practical comparison: FastAPI handles async I/O natively automatic OpenAPI generation from type hints and Pydantic validation with better error messages. For new API projects without complex admin requirements FastAPI is usually the better choice.

At Valletta Software, we focus on:

Project structure: app/api/routes/ for endpoints app/services/ for business logic app/models/ for DB models

Dependency injection: Depends() for database sessions authentication and shared services - not globals

Pydantic models: separate request schemas response schemas and DB models - dont reuse across layers

Async SQLAlchemy: AsyncSession with asyncpg - never blocking DB calls in async endpoints

Alembic migrations: autogenerate from models manual review before apply - always version-controlled

Authentication: OAuth2PasswordBearer plus JWT - fastapi-users for full auth or custom for control

Background tasks: Celery plus Redis for anything > 100ms - not FastAPI BackgroundTasks for heavy work

The Production Setup Checklist

The configuration that tutorials skip but production requires.

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Uvicorn plus Gunicorn: gunicorn with UvicornWorker - multiple workers process isolation

CORS: FastAPI CORSMiddleware with explicit origins - not allow_all in production

Rate limiting: slowapi (Limits) - protect public endpoints from abuse

Health endpoint: /health for load balancer /ready for Kubernetes readiness probe

Structured logging: structlog or python-json-logger - JSON output not print()

Environment: pydantic BaseSettings for typed config - validation at startup not runtime KeyError

OpenAPI: configure title version description - auto-generated docs are your API contract

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How to Build a Python FastAPI Backend - With Engineers Who Run It in Production

Our Python engineers build FastAPI backends with async SQLAlchemy Pydantic-typed schemas dependency injection Alembic migrations and Celery - production-ready from the first sprint.

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Our Python engineers build FastAPI backends with async SQLAlchemy, Pydantic-typed schemas, dependency injection, Alembic migrations, and Celery for background jobs.

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