Lesson 4: Real-Time Event Processing
System Design Twitter: Building Twitter's Real-Time Notification Engine
What We're Building Today
Today we transform our static Twitter clone into a living, breathing social platform. Here's what you'll accomplish:
High-Level Agenda:
Real-Time Tweet Delivery: Posts appear instantly in followers' timelines without page refresh
WebSocket Connection Management: Handle 1,000 concurrent users with persistent connections
Redis Pub/Sub Messaging: Scalable event distribution system
Event Sourcing Architecture: Complete audit trail of all user actions
Live Notifications System: Real-time alerts for likes, follows, and mentions
Production-Ready Patterns: Connection recovery, heartbeat monitoring, graceful failures
Our Mission: Build a real-time event processing system that delivers tweets to 1,000 active users within 100ms, maintains complete audit trails, and handles connection drops gracefully.
Core Concepts
Real-Time Event Processing Architecture
Real-time processing is what separates social media from traditional web applications. While a blog can wait seconds to load, Twitter users expect to see new tweets the moment they're posted. This requires fundamentally different architecture patterns.