# Design Netflix: system design interview question

> Video playback across devices: format compatibility, quality changes, peak traffic, and time-bound access to licensed titles.

Source: https://sysround.com/questions/design-netflix
Updated: 2026-11-05


Difficulty: hard. Levels: Senior, Staff+.

## How the interviewer opens it

"Design an on-demand video service for a licensed film and television catalog. Subscribers watch on different devices, including during peak demand."

## What to clarify first

- Audience
- Catalog and source files
- Devices and video quality
- Read-to-write mix
- Delivered bitrate
- Latency and playback quality
- Availability and consistency
- Rights and access
- External systems
- Scope limits

## Scope of a strong answer

Core requirements:

- Browse films, series, and episodes
- Prepare licensed source files for supported devices
- Play, pause, and seek while network speed changes
- Restrict playback to eligible subscribers within licensed countries and rights windows

Usually out of scope:

- Live broadcasts
- Offline downloads
- Recommendations and advertisements
- Account creation and payment processing
- Implementation of a DRM system

## What interviewers probe

### Playback on different devices

Devices support different formats. Network speed changes during playback. An incomplete release can break playback for only some viewers.

### Traffic during popular releases

A popular release concentrates traffic on a few titles. Empty caches and synchronized retries can overload the origin despite a high average cache hit rate.

### Access to licensed titles

Rights depend on country and time. Shared media caches must not grant access. Revocation must stop playback without a control request for every segment.

## Common mistakes

- The design treats video delivery as a database scale problem and ignores bandwidth.
- The design stores several resolutions but does not explain how the player changes quality.
- The design publishes a title before all required device formats are ready.
- The design checks access only in the application and leaves cached media or origin files unrestricted.
- The design assumes one manifest, codec, and DRM format serves every device.
- The design assumes a high average cache hit rate protects the origin during every release.

## The bar by level

- **Senior:** Explains aligned variants, atomic publication, and device compatibility. Sizes delivery and origin capacity. Handles cold releases, access renewal, revocation, and dependency failures.
- **Staff+:** Defines authority boundaries and availability trade-offs for rights checks. Quantifies delivery cost and renewal load. Plans staged provider failover. Verifies device-specific revocation guarantees.

Practice this question with an AI interviewer: https://sysround.com/practice/new?problem=subscription-video-streaming


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SysRound (https://sysround.com) is an AI practice tool for system design interviews. It has a voice or typed AI interviewer and a shared whiteboard. At the end, you get feedback on each skill and a model answer. The AI feedback can be wrong.