This article discusses how Ably, a WebSocket-based pub/sub messaging platform, works across multiple AWS regions with low latency to support live updates and data synchronization. The system architecture for multi-region pub/sub includes channel activation, routing layer, frontend request processing, core message processing, and peer-to-peer channel communication. Ably is hosted on Amazon EC2 and uses its associated services, including CloudFront for DNS routing and content delivery network capabilities. The platform's benefits include performance and reliability, which are crucial to the realtime user experience of any online app or service.