Код-ревью: сервис перед масштабированием в 4 инстанса

const sessions = new Map();
const rateLimits = {};
let orderCounter = 1000;

app.post('/login', async (req, res) => {
  const user = await auth(req.body);
  const sid = crypto.randomUUID();
  sessions.set(sid, user);
  res.cookie('sid', sid).json({ ok: true });
});

app.post('/orders', async (req, res) => {
  const ip = req.ip;
  rateLimits[ip] = (rateLimits[ip] || 0) + 1;
  if (rateLimits[ip] > 100) return res.status(429).end();
  const id = orderCounter++;
  await db.orders.insert({ id, user: sessions.get(req.cookies.sid) });
  res.json({ id });
});

app.post('/avatar', upload.single('file'), (req, res) => {
  fs.renameSync(req.file.path, './uploads/' + req.file.originalname);
  res.json({ url: '/uploads/' + req.file.originalname });
});

setInterval(sendDailyReport, 24 * 60 * 60 * 1000);