Senior Fullstack

Replace polling with Server-Sent Events (SSE) — simplest right-architecture for job notifications.

SSE is unidirectional (server → client), works over HTTP/1.1, and needs no WebSocket infra.

FastAPI SSE endpoint:

from fastapi import FastAPI
from fastapi.responses import StreamingResponse
from asyncio import Queue
import asyncio, json

subscribers: dict[str, Queue] = {}

@app.get('/notifications/{user_id}')
async def notifications(user_id: str):
    queue: Queue = Queue()
    subscribers[user_id] = queue
    
    async def event_stream():
        try:
            while True:
                event = await queue.get()
                yield f"data: {json.dumps(event)}\n\n"
        except asyncio.CancelledError:
            subscribers.pop(user_id, None)
    
    return StreamingResponse(event_stream(), media_type='text/event-stream',
                             headers={'Cache-Control': 'no-cache', 'X-Accel-Buffering': 'no'})

# Call this when a job completes:
def notify_user(user_id: str, payload: dict):
    if q := subscribers.get(user_id):
        q.put_nowait(payload)

Next.js client hook:

function useNotifications(userId: string) {
  const [events, setEvents] = useState<Notification[]>([]);
  useEffect(() => {
    const es = new EventSource(`/api/notifications/${userId}`);
    es.onmessage = e => setEvents(prev => [...prev, JSON.parse(e.data)]);
    es.onerror = () => es.close();
    return () => es.close();
  }, [userId]);
  return events;
}

Result: 0 DB polling. SSE connection stays open, ~1KB/min per connected user. For >10k concurrent users, upgrade to Redis Pub/Sub as the notification bus.