• Add static resources to Node.js server

      app.use('/static', express.static('public'));
  

• Modularize your routes, for example, in /routes/index.js:

      const express = require("express");
      const router = express.Router();
  
      router.get('/', (req, res) => {
          ...
      });
      ...
      module.export = router;
  

  Then in your main app.js

      const routes = require('./routes');
      app.use(routes);
  

• Setup CORS for your API app | npm i cors --save

      ...
      var cors = require("cors");
      ...
      app.use(cors({
          origin: ["http://localhost:8000"],
          methods: ["GET", "POST"],
          allowedHeaders: ["Content-Type", "Authorization"]
      }));
      ...
  

• Logging with Morgan | npm i morgan --save

  ...
  var morgan = require('morgan');
  ...
  app.use(morgan('common'));
  

• Configuring Node.js clusters in cluster.js | Clusters

      var cluster = require("cluster");
      var os = require("os");
      
      const CPUS = os.cpus();
      
      if (cluster.isMaster) {
          for (var i = 0; i < CPUS.length; i++) { 
              cluster.fork() 
          });
          
          cluster.on("listening", function(worker) {
              console.log(`Cluster ${ worker.process.pid } connected`);
          });
      
          cluster.on("disconnect", function(worker) {
              console.log(`Cluster ${ worker.process.pid } disconnected`);
          });
  
          cluster.on("exit", function(worker) {
              console.log(`Cluster ${ worker.process.pid } is dead`);
              // Ensuring a new cluster will start if an old one dies
              cluster.fork();
          });
      } else {
          require("./index.js");
      }
  

  Then run: nodemon cluster.js

• GZIP Compression | npm i compression --save | Compression

      ...
      var compression = require('compression');
      ...
      app.use(compression(6)); // number indicates level of compression
  

  
  

• Protect from some forms of attach with Helmet | npm i helmet --save

      ...
      var helmet = require('helmet');
      ...
      app.use(helmet());
  

Credit: JScrambler Blog