A Client-Side Routing developer is responsible for managing navigation within a single-page application. They create and implement routing structures using JavaScript frameworks like React, Angular, or Vue.js. The developer ensures that the application behaves consistently and efficiently, loading and displaying appropriate content based on the user's interaction without refreshing the entire page. They handle URL changes, manage states, and deal with the history stack to provide a seamless user experience. They also ensure the application is search engine friendly by implementing strategies like server-side rendering or pre-rendering.