Design TikTok
PremiumProduct architectureMedium
- Short video feed
- Video prefetching
- Recommendation serving
Quick answer
This product architecture interview question asks you to design TikTok. 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 TikTok, a short-video app where people swipe through an endless For You feed of clips chosen for them and upload their own videos. The hard parts are starting each video instantly on swipe, serving feeds to hundreds of millions of people, and feeding watch signals back to ranking within minutes.
What must the system do?
- For You feed: An endless vertical feed, fetched 10 videos at a time, never showing a video the user already watched in the last 30 days.
- Instant playback: The next video starts playing within 200 ms of a swipe.
How well must it do it?
- Smooth swiping: Fewer than 1% of swipes show a loading spinner.
- Feed latency: A feed page returns in under 300 ms at p99, including the ranking call.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Short video feed
- Video prefetching
- Recommendation serving
- Event streaming
- CDN
- Bloom filter
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 TikTok 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