A little bit of context: I have completed projects and created my resume. I am prepared for interviews in terms of projects. However, it seems that they usually ask theoretical questions such as "What is the Event Loop?" or "What are streams?" For those who have experience in conducting or participating in interviews, what do you think are the important topics and questions I should be prepared for?

Additionally, I primarily work on the backend using Node.js. I have previously used React.js in past projects, but I found frontend development to be challenging, which led me to shift my focus. However, I am capable of implementing a full-stack web application if a frontend template is provided. Should I also prepare for advanced theoretical questions (beyond the basics) on React? If so, what are the key areas I should focus on at a minimum?