text: const crypto = require('crypto');
  function hash(password, cb) {
      const salt = crypto.randomBytes(128).toString('base64');
      const hash = crypto.pbkdf2(password, salt, 10000, 512, 'sha512', cb);
      return hash;
  }
  // Imagine that loop below is real requests to some route
  for (let i = 0; i < 50; i++) {
      hash('tips_tricks', (error, hash) => {});
  }