auto increment with two queries

model.js

var mongoose = require('mongoose');

var counter = mongoose.Schema({
    type: { type: String, index: { unique: true }},
    seq: Number
});

// create the model for users and expose it to our app
module.exports = mongoose.model('counter', counter);

mongo-auto-inc-id.js

    var getNextInvoiceNumber = function getNextInvoiceNumber(name , cb) {

        var temp = new counter();
        temp.seq = 1;
        temp.type = name

        temp.save(function (err , result) {
            if(!err){
                cb(1);
            } else {
                counter
                    .findOneAndUpdate( {type: name},
                    {$inc: {seq: 1}})
                    .exec(function (err, db_res) {
                       cb(db_res.seq)
                    });
            }
        })

    }