Art of Codeartofcode
Lesson 7 of 16

40. Design Video Upload and Streaming (YouTube)

1
The interview prompt
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40.1 What do you ask first?
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40.2 How big is this, really?
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40.3 What are the doors?
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40.4 What do we store?
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40.5 What does the whole system look like?
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40.6 How does the upload pipeline work?
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40.7 How does transcoding work?
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40.8 How does adaptive bitrate work?
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40.9 How does CDN delivery work at this scale?
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40.10 How do you count views?
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40.11 What would you say in the last five minutes?
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Score yourself
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Variations to practise
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Sources
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Code lab
40. Design Video Upload and Streaming (YouTube)

40.6 How does the upload pipeline work?

3 min read+10 XP

Step 5: Deep dives (10 minutes)

  • Direct to storage: the API hands out a signed upload URL (Chapter 11); gigabytes never pass through app servers.
  • Resumable: the file goes in chunks (say 8 MB). If the connection drops, the client asks "what do you have?" and sends only the rest. In the chapter's code, a 2 GB upload that drops after 180 chunks resumes with the last 70, not from zero.
  • Validate early: check the format and duration before spending transcoding money; reject corrupt or disallowed files.
  • Status the creator can see: uploading → processing (with progress) → ready (or failed, with a reason).

Memory code: "Upload in pieces, resume from the gap, check before you spend."