Node.js is one of those things that not only allows you to have a much more responsive web application, but it can also greatly help with your development time and make your applications able to handle far more traffic than they otherwise would be able to do if you didn't use Node.This makes it perfect for using in conjunction with any kind of heavy database such as MongoDB or Cassandra, along with large numbers of users visiting your site all at once. Some companies that use Node are Netflix, LinkedIn, Zynga, and PayPal just to name a fewWalmartUberSlackPayPalNetflixTwitterRedditGrouponGoDaddyTrelloCitibankMediumeBayNASALinkedin