Discord: Scaling Elixir, Rust, & ScyllaDB for Millions of Concurrent Users
Power millions of simultaneous voice/text channels: Elixir BEAM processes, Rust NIF memory safety, migrating from Cassandra to ScyllaDB, and WebSocket gateway scaling.
01.1. The Real-Time Community Scale of Discord
Discord powers real-time communication for over 150 million monthly active users and hundreds of thousands of concurrent gaming, developer, and creator communities. Unlike standard social feeds where users passively scroll, Discord is an intensely interactive real-time environment:
- Millions of users participate simultaneously in voice calls, video streams, and text channels.
- Over 10 million persistent WebSocket connections are held open concurrently across global gateway clusters.
- Billions of messages are read, written, and fanned out in real time every day.
To achieve extreme concurrency with low latency, Discord engineered a hybrid technology stack combining Elixir, Rust, and ScyllaDB.
Discord Real-Time Chat & Storage Architecture 💬
Discord Real-Time Chat & Storage Architecture 💬
Elixir BEAM WebSocket gateways paired with Rust NIF acceleration and ScyllaDB C++ distributed storage rings.
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