The interview focused on deep knowledge of React and JavaScript fundamentals. I was asked about how React works internally, including React Fiber, the virtual DOM, rendering, reconciliation, and different ways of managing state. On the JavaScript side, questions covered prototypes, closures, context, the event loop, and promises with their utility functions. The process also included basic web security topics such as common attacks and CORS policies, as well as software design principles, including design patterns and the application of SOLID.