First time it saves client to database and second time it gives 500 error

[penubothuvenkannacho]

 Client.findOne({ email: req.body.email }, function (err, user) {
        console.log(user);
   
      // Make sure user doesn't already exist
      if (user) return res.status(400).send({ msg: 'The email address you have entered is already associated with another account.' });
   
      // Create and save the user
     Client.create({ username: req.body.name, email: req.body.email, phone: req.body.phone, password: req.body.password }, function(err, client) {
          if (err) { return res.status(500).send({ msg: err.message }); }
          console.log(client);

          // Create a verification token for this user
          var token = new Token({ _userId: client._id, token: crypto.randomBytes(16).toString('hex') });
   
          // Save the verification token
          token.save(function (err) {
              if (err) { return res.status(500).send({ msg: err.message }); }
});

[m_hutley]

What is Client? what is Token? Where are you getting these object definitions from? What kind of database are you writing to?

[penubothuvenkannacho]

I have defined schema definitions in another file then I am creating instance of them.

The problem got solved it occurs due to duplicate indexes.