You've designed media streaming systems.
YouTube: User uploads → transcoding pipeline → multiple formats/resolutions → CDN delivery → adaptive streaming.
Netflix: Pre-encoded content → Open Connect CDN inside ISPs → heavy personalization.
Spotify: Small audio files → aggressive local caching → predict next songs.
All use CDNs for global delivery. All use chunked streaming for adaptability. Next, you'll design hard problems: payments and e-commerce.