# Design a screen sharing service: system design interview question

> Live screen delivery with readable text, low delay, and different network limits for each viewer.

Source: https://sysround.com/questions/design-screen-sharing-service
Updated: 2026-11-05


Difficulty: hard. Levels: Senior, Staff+.

## How the interviewer opens it

"Design a service that shares a user's screen with remote participants. Keep text readable and delay low when network capacity changes."

## What to clarify first

- Session size
- Scale and clients
- Screen content
- Traffic mix
- Delay
- Network limits and quality
- Geographic scope
- Consistency and durability
- Privacy and access
- Exclusions

## Scope of a strong answer

Core requirements:

- Share a selected screen or application window
- Let authorized participants view the active share
- Adapt screen delivery to each viewer's network limits
- Stop screen delivery when the presenter ends the share

Usually out of scope:

- Audio and camera video
- Remote mouse and keyboard control
- Recordings and playback
- Calls across continents
- End-to-end encryption

## What interviewers probe

### Text quality

Text needs sharp edges, but motion consumes much more bandwidth. A policy that favors smooth motion can make the shared screen unreadable.

### Different viewer networks

One source serves viewers with different network and decode limits. A slow viewer must not create long delays or reduce quality for everyone.

### Viewer growth and recovery

Viewer growth increases service traffic without changing the source screen. New viewers and failed media servers still need a complete, decodable image.

### Screen access

A screen can expose private data immediately. An open media connection can outlast the permission that allowed it.

## Common mistakes

- Treats the screen as a file stream with no limit on frame age.
- Lowers resolution before frame rate, which can make text unreadable.
- Assumes an SFU can create readable media at a lower rate by removing arbitrary packets.
- Budgets media bandwidth but ignores extra source layers and TURN traffic.
- Stores screen frames without a requirement or a privacy policy.
- Checks access only when a viewer joins.

## The bar by level

- **Senior:** Separates control from media. Defines rate control for each viewer, bounded queues, and recovery from missing frames. Budgets source upload, media fanout, and relay traffic.
- **Staff+:** Defines a client support policy and measurable quality goals. Resolves conflicts between text quality and delay. Handles revocation failures and regional recovery. Justifies the cost of extra encodes and spare media capacity.

Practice this question with an AI interviewer: https://sysround.com/practice/new?problem=screen-sharing


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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.