// Example middleware for idempotency async function idempotencyMiddleware(req: Request, res: Response, next: NextFunction){const key=req.header('Idempotency-Key'); if(!key)return res.status(400).json({ error: 'Idempotency-Key required' }); const cached = await redis.get(idemp:${key}); if (cached) return res.json(JSON.parse(cached)); }