Live chat is a common realtime web experience that has become essential for businesses to provide faster customer support and improve user engagement. Realtime messaging systems are critical in delivering live chat experiences, as they ensure instant or near-instant message receipt and delivery. The challenges of scaling realtime messaging for chat use cases include ensuring message delivery across disconnections, achieving consistently low latencies, dealing with volatile demand, architecting the system for scale, and making it fault tolerant. To overcome these challenges, best practices such as preserving data integrity, using a low-latency protocol like WebSocket, choosing horizontal over vertical scaling, and utilizing an architecture pattern designed for scale like pub/sub are recommended.