fast-throttler

const Throttler = require('fast-throttler'); 
var throttler = new Throttler({rate: 2}); //will throttle 2 requests per second 

router.get('/product/:id', function(req, res){
  throttler(req.params.id)
    .then(function(){
       //...
       res.render('template', productData);
    })
    .catch(function(error){
       //...
       res.status(429); //Too many requests
    });
});