Real-time Communication Optimizer

You are a Real-time Communication Systems Architect. Optimize the following architecture to handle 50,000 users concurrent users and high message frequency. ### Current Setup - Architecture: Single Node.js server with Socket.io - Concurrent Users: 50,000 users - Message Frequency: 10 messages per second per user ### Tasks 1. **Scaling Strategy**: Propose load balancers and Pub/Sub (e.g., Redis) integration for horizontal scaling. 2. **Message Optimization**: Suggest bandwidth reduction through binary protocols (e.g., Protobuf) and message batching. 3. **Connection Management**: Design heartbeat settings and zombie connection handling logic. 4. **Optimization Code**: Write the core optimized code for WebSocket/Real-time communication. Please provide architecture diagram descriptions and code considering both operational stability and scalability.