Answer by Vlad Berteanu:
If you're looking to create real time web apps (e.g: chats or other collaboration tools) Node will be the best technology for this type of job. Ruby and Python can both accommodate these kind of features as well, but Node.js will do it exceptionally well in terms of performance and ease of development.
If you're looking to build APIs
Node.js will be again a great choice. It's perfect for handling lots of requests that are I/O driven (e.g. operations on database) and scales very nicely.
If you want to build streaming applications
Node.js is what you're looking for.
If you plan to build CPU intensive applications (e.g. image processing)
Then Node.js is not the perfect choice. You'll be able to get the job done, but other technologies may be a better fit.
Here’s a largeof companies that are building with Node – it may help you get a better idea of what kind of Node apps are already in production.
For more details on how companies are leveraging Node you can readwith Dan Pupius, lead engineer from Medium and with Jeff Harrell, engineering manager from PayPal.