test.js

const express = require('express')
const app = express()
const port = 2709

app.get('/home', (req, res) => res.send('Hello Zetwerk'))

app.get('/test', async (req, res) => {
  await doSomeLongOperation();
  res.send('Operation is done')
})

app.use(function (req, res, next) {
  res.status(404).send('Sorry can\'t find that!')
})


async function doSomeLongOperation() {
  for (let i = 0; i < 5000000000000; i++) {
    console.log(await square(i))
  }
}

async function square(i) {
  return new Promise(resolve => setTimeout(function () {
    resolve(i*i)
  }, 1000)
  )
}

app.listen(port, () => console.log(`App listening on port ${port}`))

If we want to do some complex operation instead of the square function, we can offload it by using worker threads | child process | cluster | N-API native node addons (C/C++).