httpx

Migrating from Flask or Django to FastAPI requires replacing familiar tools: `requests` must be replaced with `httpx` for async operations, Django REST Framework serializers must become Pydantic models, and the async paradigm shift is non-trivial. FastAPI lacks the built-in ORM and admin panel developers relied on.

Developers frequently block event loops with sync I/O calls (e.g., using `requests` instead of `aiohttp`), throttling async performance. Missing `await` keywords cause runtime exceptions rather than compile-time hints.