server.js

const express = require('express');
const next = require('next');
const port = parseInt(process.env.PORT, 10) || 3000;
const dev = process.env.NODE_ENV !== 'production';
const app = next({ dev });
const handle = app.getRequestHandler();
const Cache = require('lru-cache');

const ssrCache = new Cache({
 max: 20, // not more than 20 results will be cached
 maxAge: 1000 * 60 * 5, // 5 mins
});


async function renderAndCache(req, res, pagePath, queryParams) {
 const key = req.url;
 // if page is in cache, server from cache
 if (ssrCache.has(key)) {
  res.setHeader('x-cache', 'HIT');
  res.send(ssrCache.get(key));
  return;
 }
 try {
  // if not in cache, render the page into HTML
  const html = await app.renderToHTML(req, res, pagePath,
  queryParams);
  
  // if something wrong with the request, let's skip the cache
  if (res.statusCode !== 200) {
   res.send(html);
   return;
  }
  ssrCache.set(key, html);
  
  res.setHeader('x-cache', 'MISS');
  res.send(html);
 } catch (err) {
  app.renderError(err, req, res, pagePath, queryParams);
 }
}

app.prepare().then(() => {
 const server = express();
 server.get('*', (req, res) => handle(req, res));
 server.listen(port, (err) => {
  if (err) throw err;
  console.log(`🤘 on http://localhost:${port}`);
 });
});