Express.js

Express.js, or simply Express, is a back end web application framework for Node.js, is fast, robust, and asynchronous in nature, and designed for building web applications and APIs. The primary use of Express is to provide server-side logic for web and mobile applications.  

This competency area covers an understanding of nested routers, express rate limit, cookies, among others. 

Key Competencies: 

1. Nested Routing - Understanding the usage and importance of nested routes and understanding of how an application’s endpoints (URIs) respond to client requests. 
2. Handling Cookies - Handling Cookies with Express using a third party npm package (e.g. cookie-parser).
3. API Throttling - Understanding API Throttling and Rate Limiting in Express.js. Express Rate Limit is an npm package which provides a flexible rate limiting middleware.
4. Asynchronous File Uploads - Ability to perform asynchronous file uploads, by setting up required libraries and packages.