Fastapi Async Patterns

This one covers the patterns you need for async FastAPI, from basic route handlers to WebSocket connections. It shows you when to use async versus sync endpoints (IO-bound versus CPU-bound), how to wire up async database operations with SQLAlchemy, asyncpg, and Motor, and how to handle background tasks without blocking responses. The WebSocket section includes a connection manager for broadcasting, which is what you'll need for chat apps or live dashboards. Honestly, the value here is having working examples of the dependency injection patterns and session management rather than hunting through docs. If you're moving from sync Flask or building something that needs to handle thousands of concurrent connections, this gives you the patterns to do it right.

skills.sh installs: 958
GitHub stars: 200
last updated: Aug 21, 2026

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Install

$ npx -y skills add thebushidocollective/han --skill fastapi-async-patterns --agent claude-code

Installs into .claude/skills of the current project.

Files

FastAPI Async Patterns

Master async patterns in FastAPI for building high-performance, concurrent APIs with optimal resource usage.

Basic Async Route Handlers

Understanding async vs sync endpoints in FastAPI.

from fastapi import FastAPI
import time
import asyncio

app = FastAPI()

# Sync endpoint (blocks the event loop)
@app.get('/sync')
def sync_endpoint():
    time.sleep(1)  # Blocks the entire server
    return {'message': 'Completed after 1 second'}

# Async endpoint (non-blocking)
@app.get('/async')
async def async_endpoint():
    await asyncio.sleep(1)  # Other requests can be handled
    return {'message': 'Completed after 1 second'}

# CPU-bound work (use sync)
@app.get('/cpu-intensive')
def cpu_intensive():
    result = sum(i * i for i in range(10000000))
    return {'result': result}

# I/O-bound work (use async)
@app.get('/io-intensive')
async def io_intensive():
    async with httpx.AsyncClient() as client:
        response = await client.get('https://api.example.com/data')
        return response.json()