A full stack JavaScript backend developer is a programmer who has the skills and knowledge to work on both the front-end and back-end of web development using JavaScript-based technologies. Here are some of the commonly used technologies in the stack:

Node.js is a JavaScript runtime built on the Chrome V8 engine. It allows developers to use JavaScript on the server-side, which makes it possible to create highly scalable and efficient web applications. Full stack developers who work with Node.js have expertise in building APIs, web applications, and microservices.

Next.js is a React-based web framework that provides server-side rendering capabilities for React applications. It allows developers to build highly performant web applications that load quickly and are optimized for search engines. Full stack developers who work with Next.js have expertise in building SEO-friendly web applications, as well as developing custom themes and plugins for Next.js-based applications.

Express.js is a minimal and flexible Node.js web application framework that provides a range of features for building web applications and APIs. It allows developers to easily handle HTTP requests, manage sessions, and implement security features. Full stack developers who work with Express.js have expertise in building RESTful APIs and web applications using this framework.

Backbone.js is a lightweight JavaScript library that provides a range of features for building single-page applications. It provides a simple and intuitive API for managing data models and views. Full stack developers who work with Backbone.js have expertise in building highly interactive single-page applications.

Meteor.js is a full-stack JavaScript framework that provides a range of features for building web and mobile applications. It includes built-in support for real-time data synchronization, server-side rendering, and database management. Full stack developers who work with Meteor.js have expertise in building real-time web and mobile applications.

Overall, full stack developers who work with Node.js, Next.js, Express.js, Backbone.js, and Meteor.js have a wide range of skills and knowledge related to web development using JavaScript. They are able to work on both the front-end and back-end of web applications, and they can develop custom functionality and features using their expertise in these technologies. They also have a good understanding of database management, security, and other important aspects of web development.