I started by defining core components like user registration, video storage, and playback. The interviewer engaged with my thoughts on using CDN for efficient delivery but pushed back on scaling concerns as user base grows. I suggested microservices for better management but struggled a bit with database selection when asked about handling metadata for millions of videos. The discussion veered into specifics about video encoding and adaptive streaming, which I wasn't as confident about and felt that affected the overall flow of my explanation.