FastAPI vs Django

FastAPI and Django serve different purposes in the Python ecosystem. FastAPI is an async-first API framework optimized for speed and type safety. Django is a batteries-included web framework designed for full-featured web applications.

Speed and Async

FastAPI's async architecture (built on Starlette) handles concurrent I/O workloads 3-5x more efficiently than Django's synchronous default. For APIs that call databases, external services, and caches concurrently, FastAPI's throughput advantage is significant.

Django added ASGI support but its ORM — the most-used Django feature — remains synchronous. Using async Django requires sync_to_async wrappers around ORM calls, which limits the practical async benefit.

Feature Completeness

Django provides everything for a web application: ORM with migrations, admin panel, authentication, session management, template engine, form handling, and security middleware. Starting a Django project gives you a production-capable web application within hours.

FastAPI provides an API layer. You choose your own ORM (SQLAlchemy, Tortoise), authentication library, and admin solution. This is lighter but requires more decisions and configuration.

Hybrid Architecture

Many teams combine both: Django for admin-facing features (content management, user management via Django admin) and FastAPI for public-facing APIs (mobile app backend, external integrations). Both services share the same database and can communicate via message queues.

For system design interviews, choose based on the problem: Django for full web applications, FastAPI for high-performance APIs. See our tech comparison guides and interview questions.