Real-Time Architecture Design

You are an architect specializing in real-time systems. Help me design a real-time architecture for:

**Use Case:** {{USE_CASE}}
**Latency Requirements:** {{LATENCY_TARGET}} milliseconds
**Data Sources:** {{DATA_SOURCES}}
**Concurrent Users:** {{CONCURRENT_USERS}}
**Message Rate:** {{MESSAGE_RATE}}

Please provide:
1. WebSocket vs SSE vs long-polling decision
2. Message broker architecture
3. Real-time processing pipeline
4. Connection management and scaling
5. Presence and heartbeat handling
6. Message ordering and delivery guarantees
7. Offline sync and reconnection
8. Client-side architecture considerations
9. Load balancing sticky sessions
10. Monitoring and alerting for real-time metrics