It looks like JavaScript is taking the crown from Ruby for modern web development. I never used it in the backend, so I was curious to research about the libraries and frameworks that the cool kids are using these days. Here are some of them:

node.js – event-driven runtime environment for developing server-side applications . Allows you to develop in JS, and it’s quite fast. It also handles concurrent connections quite efficiently.

express.js – minimalist server-side web framework for node.js

React – javascript library for building user interfaces

angular.js – client-side, web applications framework, especially suitable for single-page applications

knex.js – SQL query builder for JavaScript

backbone.js – javascript library with a RESTful JSON interface, based on MVP

socket.io – javascript library for real time web apps. enables biderection communication between server and client

As for databases, MySQL seems to still be the default choice, by MongoDB and PostgreSQL are following closely.

Here’s an interesting post about the topic (though from 2014): Which Technologies Do Startups Use? An Exploration of AngelList Data