Telegram Sends Duplicate Responses — Webhook Retry Causes Double Processing
Symptom
- User sends one message, bot responds twice
- Second response usually arrives 3–5 seconds after the first
- Only happens under load or when processing is slow (>5s)
- Does not happen in polling mode — only webhook mode
Root Cause
Telegram’s webhook delivery requires a 200 OK response within 5 seconds. If your agent takes longer (e.g., LLM inference + tool calls), Telegram retries delivery. Without message deduplication, the agent processes and responds to the same message twice.
Fix
Option 1: Respond 200 immediately, process async
from fastapi import FastAPI, Request, BackgroundTasks
app = FastAPI()
@app.post("/webhook")
async def webhook(request: Request, background_tasks: BackgroundTasks):
update = await request.json()
# Respond to Telegram immediately
background_tasks.add_task(process_update, update)
return {"ok": True} # 200 within milliseconds
async def process_update(update):
# Process here — Telegram doesn't wait for this
await agent.handle(update)
Option 2: Deduplicate by update_id
import asyncio
from collections import deque
_processed_ids = deque(maxlen=10000)
async def webhook(update):
update_id = update.get('update_id')
if update_id in _processed_ids:
return # Already processed — discard duplicate
_processed_ids.append(update_id)
await process_update(update)
Option 3: Redis-based deduplication (for multi-replica deployments)
import redis.asyncio as redis
r = redis.Redis()
async def webhook(update):
update_id = str(update['update_id'])
was_set = await r.set(f"update:{update_id}", "1", nx=True, ex=300)
if not was_set:
return # Another replica already processed this
await process_update(update)
Expected Token Savings
Debugging duplicate response issue: ~8,000 tokens This fix: ~200 tokens to implement
Environment
- Telegram Bot API (webhook mode)
- Any Python/Node.js agent backend
- Source: direct experience, common pattern in Telegram bot development
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