Design a Real-Time Video Conferencing System

Problem

Design Zoom's core: a real-time video conferencing system for low-latency multi-party calls.

Requirements

Functional:

• Multi-party audio/video with low latency
• Screen share and recording
• Scale a meeting to thousands of participants
• Adapt to network conditions

Non-functional:

• Millions of concurrent meetings
• Sub-200ms media latency
• Resilient to packet loss

Discussion points

1. SFU vs MCU vs mesh topology trade-offs
2. Media servers and routing
3. Adaptive bitrate / simulcast and packet-loss concealment
4. Signaling vs media planes
5. Recording and scaling large meetings