Design YouTube
PremiumProduct architectureMedium
- Video transcoding
- Adaptive bitrate streaming
- HLS
Quick answer
This product architecture interview question asks you to design YouTube. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Design YouTube, a video platform where creators upload videos and viewers watch them on any device and network. The hard parts are turning each upload into many streamable versions quickly and delivering about 100 Tbps of video without overloading origin storage.
What must the system do?
- Upload: A creator uploads a file of up to 256 GB or 12 hours, and the upload resumes after a network drop without starting over.
- Watch: A viewer presses play and the video starts in under 2 seconds, with quality switching automatically as the network changes.
How well must it do it?
- Fast start: Time to first frame under 2 seconds at p90, and rebuffering under 1% of watch time.
- No lost uploads: An upload acknowledged as complete is never lost, and failed processing steps are retried.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Video transcoding
- Adaptive bitrate streaming
- HLS
- CDN
- Resumable uploads
- View counting
How you’ll practise
- Requirements
- Core entities
- API design
- Client and server flow
- Scale and edge cases
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any product architecture design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a product architecture question. You design YouTube and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the requirements: what the system must do, how well it must do it and which numbers change the design. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team