python-backend

name	python-backend
license	MIT
compatibility	Claude Code 2.1.76+.
description	Production Python async patterns including asyncio TaskGroup, FastAPI dependency injection and middleware, SQLAlchemy 2.0 async sessions, and database connection pool tuning. Python 3.11+ examples with structured error handling. Use when building async services, FastAPI endpoints, or tuning database connection pools.
tags	["python","asyncio","fastapi","sqlalchemy","connection-pooling","async","postgresql"]
context	fork
agent	backend-system-architect
version	2.0.0
author	OrchestKit
user-invocable	false
disable-model-invocation	false
complexity	medium
persuasion-type	reference
targets	[{"library":"fastapi","version":">=0.100.0"},{"library":"sqlalchemy","version":">=2.0.0"}]
metadata	{"category":"document-asset-creation"}
allowed-tools	["Read","Glob","Grep","WebFetch","WebSearch"]
path_patterns	["*.py","**/requirements*.txt","**/pyproject.toml","**/Pipfile"]

Python Backend

Patterns for building production Python backends with asyncio, FastAPI, SQLAlchemy 2.0, and connection pooling. Each category has individual rule files in rules/ loaded on-demand.

Quick Reference

Category	Rules	Impact	When to Use
Asyncio	3	HIGH	TaskGroup, structured concurrency, cancellation handling
FastAPI	3	HIGH	Dependencies, middleware, background tasks
SQLAlchemy	3	HIGH	Async sessions, relationships, migrations
Pooling	3	MEDIUM	Database pools, HTTP sessions, tuning

Total: 12 rules across 4 categories

Quick Start

# FastAPI + SQLAlchemy async session
async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise

@router.get("/users/{user_id}")
async def get_user(user_id: UUID, db: AsyncSession = Depends(get_db)):
    result = await db.execute(select(User).where(User.id == user_id))
    return result.scalar_one_or_none()

  () -> []:
      asyncio.timeout():
          asyncio.TaskGroup()  tg:
            tasks = [tg.create_task(fetch_url(url))  url  urls]
     [t.result()  t  tasks]