How Discord Handles Two and Half Million Concurrent Voice Users Using WebRTC
Article Summary
Discord handles 2.6 million concurrent voice users with just 850 servers across 13 regions. Here's how they built a custom WebRTC architecture that scales.
Discord's engineering team shares their technical approach to real-time voice and video communication. Written by Staff Engineer Jozsef Vass, this deep dive reveals how they modified WebRTC to serve millions of gamers while keeping IP addresses private and bandwidth costs low.
Key Takeaways
- Custom C++ media engine bypasses WebRTC's SDP/ICE/DTLS for 90% smaller handshakes (1KB vs 10KB)
- Salsa20 encryption replaces DTLS/SRTP for faster performance and silence suppression
- Client-server architecture prevents IP leaks and enables moderation at scale
- Homegrown SFU bridges native and browser clients while dropping packets from muted users
- Elixir-based signaling servers with etcd service discovery enable zero-downtime failovers
Critical Insight
Discord serves 220 Gbps of voice traffic by customizing WebRTC's lower-level APIs and building specialized infrastructure that prioritizes gaming use cases over standard implementations.
