Multi-AZ stock streaming system with 30k concurrent users leveraging WAF, CloudFront CDN, Route 53, and ALB to distribute WebSocket connections across two availability zones. Web and mobile clients route through AWS security and caching layers to four WebSocket servers that ingest market data into Kafka brokers with ZooKeeper coordination, ensuring fault tolerance and low-latency message delivery. Stream consumers feed price aggregation logic into Redis caching and PostgreSQL with TimescaleDB for time-series analytics, while Alert Engine monitors anomalies via CloudWatch and S3 archives historical data. This architecture demonstrates production-grade patterns for real-time financial data platforms requiring sub-second latency, automatic failover, and horizontal scaling across AZs.