Youtube

Questions

What features are important? (Upload a video, watch a video)
What clients do we need to support? (Mobile apps, web browsers, smart TV)
What is the maximum allowed video size? (1GB)
What are the supported video resolutions? (Most video resolutions and formats)
What is the average daily time spent on the product? (30 minutes)

Who are our users? (5 million daily active users, including a large percentage of international users)

How is encryption handled? (Encryption is required)
How can we leverage existing infrastructure? (Use cloud services from Amazon, Google, or Microsoft)

The entire system is broken down in two parts: video uploading flow and video streaming flow.

Original storage:
- A blob storage system is used to store original videos.
- “A Binary Large Object (BLOB) is a collection of binary data stored as a single entity in a database management system”
Transcoding servers:
- Video transcoding is also called video encoding. It is the process of converting a video format to other formats (MPEG, HLS, etc), which provide the best video streams possible for different devices and bandwidth capabilities.
Transcoded storage: It is a blob storage that stores transcoded video files.
CDN: Videos are cached in CDN. When you click the play button, a video is streamed from the CDN.
Completion queue: It is a message queue that stores information about video transcoding completion events.
Note: Downloading means the whole video is copied to your device, while streaming means your device continuously receives video streams from remote source videos.
- When you watch streaming videos, your client loads a little bit of data at a time so you can watch videos immediately and continuously.
- different streaming protocols support different video encodings and playback players. When we design a video streaming service, we have to choose the right streaming protocol to support our use cases