Building Discord : From Socket to Scale

Course Details

Why This Course? Most system design resources focus on stateless request/response models (like a Twitter feed or e-commerce cart). But the modern web is real-time. This course fills the critical gap between “building a chat app with socket.io” (which takes a weekend) and “engineering a high-concurrency real-time platform” (which takes a career). We move beyond simple polling to mastering persistent connections, handling the “Thundering Herd,” and managing stateful services at a massive scale.

What You’ll Build You will build “Flux,” a fully functional distributed chat platform. We start with a single script sending messages and end with a distributed, sharded, microservices-based platform featuring a custom Gateway, Pub/Sub Fan-out logic, Voice SFU routing signaling, and a specialized Cassandra-like storage engine for infinite chat history.

Who Should Take This Course? This is for engineers tired of “Toy Apps.” Whether you are a fresh grad wanting to understand how WebSocket clusters work, a backend engineer looking to transition into distributed systems, or a Product Manager wanting to understand why “read receipts” are technically expensive at scale.

Key Topics Covered: Persistent WebSockets, Stateful Load Balancing, Consistent Hashing Rings, Pub/Sub Fan-out, Wide-Column Database Modeling (LSM Trees), Voice/Video Signaling (WebRTC & SFU), Rate Limiting Distributed Traffic (Redis Lua), and Ring Buffers for message replay.