Design a mobile video streaming app like Netflix
PremiumMobile systemMedium
- HLS
- Adaptive bitrate streaming
- Offline downloads
Quick answer
This mobile system interview question asks you to design a mobile video streaming app like Netflix. 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 a mobile video streaming app like Netflix for iOS and Android. Users browse a catalog, stream shows that adapt to the network, download episodes to watch offline and pick up where they left off on another device. The hard parts are fast playback start, adaptive quality on mobile networks and DRM-protected downloads that expire.
Video is already encoded and served from a CDN. Design the app.
What must a mobile video streaming app like Netflix do?
- Stream: Play any title with quality that adapts to the network, without stalls.
- Download: Download episodes in Standard or High quality and play them with no network.
How well must it do it?
- Fast start: Video starts within 2 seconds of tapping Play on a 5 Mbps network.
- Few stalls: Under 1% of viewing time spent rebuffering.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- HLS
- Adaptive bitrate streaming
- Offline downloads
- FairPlay
- Widevine
- Playback position sync
How you’ll practise
- Requirements
- App architecture
- Data and offline sync
- Networking and push
- Performance, battery and releases
- 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 mobile system 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 mobile system question. You design a mobile video streaming app like Netflix 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