In streaming your website is typically totally divorced from your media serving. Media serving is just a question of cloud storage and pointing at an hls/dash manifest in that object store. Once it starts playing the website itself does almost nothing. Live streaming adds more complexity but it's still not much of a website problem.

Maintaining the media lifecycle, receiving, transcoding, making it available and removing it, is the big task but that's not real-time, it's batch/event processing at best efforts.

The biggest challenges with streaming are maintaining the content catalogue, which aren't just a few million records but rich metadata about the lifecycle and content relationships. Then user management and payments tends to also have a significant overhead, especially when you're talking about international payment processing.