He clonado un repositorio de GitHub como referencia. Pero no sé a qué se refiere este .keys_dev. Todo me parece bien. Pero me está devolviendo error. Todo está en su lugar como se esperaba. Espero que alguien pueda ayudarme. Requiere una pila que es desconocida para mí. Requiere una API que ya está definida. Necesito entender ¿alguien puede ayudarme?

 const express = require("express"); const bodyPaser = require('body-parser'); const mongoose = require('mongoose'); const passport = require('passport'); const path = require('path'); const cors = require('cors'); const users = require('./routes/api/users'); const level = require('./routes/api/levels'); const employee = require('./routes/api/employees'); const exception = require('./routes/api/exception'); const payslip = require('./routes/api/payslip'); const dashboard = require('./routes/api/dashboard'); const individualcost = require('./routes/api/individualcost'); const oneoffpayment = require('./routes/api/oneoffpayment'); const record = require('./routes/api/record'); const app = express(); //Body parser middleware app.use(bodyPaser.urlencoded({ extended: false })); app.use(bodyPaser.json()); app.use(cors()) //Db const db = require("./config/keys").mongoURI; //MongoDB connection mongoose .connect( db, { useNewUrlParser: true } ) .then(() => console.log("MongoDB connected")) .catch(err => console.log(err)); //Passport Middleware app.use(passport.initialize()); //Passport config require('./config/passport')(passport); //Use routes app.use('/api/users', users); app.use('/api/level', level); app.use('/api/employee', employee); app.use('/api/exception', exception); app.use('/api/payslip', payslip); app.use('/api/dashboard', dashboard); app.use('/api/individualcost', individualcost); app.use('/api/oneoffpayment', oneoffpayment); app.use('/api/record', record); // Server static assets if in production if (process.env.NODE_ENV === 'production') { // Set static folder app.use(express.static('client/build')); app.get('*', (req, res) => { res.sendFile(path.resolve(__dirname, 'client', 'build', 'index.html')); }); } const PORT = process.env.PORT || 5000; app.listen(PORT, () => console.log(`App is running on port ${PORT}`));