Python Backend

Production async Python patterns that actually matter: TaskGroup over gather() for structured concurrency, FastAPI dependency injection the right way, and SQLAlchemy 2.0 async sessions with proper pooling. The anti-patterns section alone is worth it, calling out real bugs like sharing AsyncSession across tasks and swallowing CancelledError. Covers the essentials from asyncio.timeout() context managers to connection pool sizing formulas. Use this when you're building FastAPI services and want to avoid the common async footguns that lead to race conditions and event loop blocking. Assumes Python 3.11+ and modern library versions.