Implementing stream continuity over a distributed realtime messaging system

The Ably team has developed a solution for handling changing connectivity state in realtime messaging systems. They have tackled the challenge of connection state and stream continuity, which is essential for applications like chat functionality. Their approach involves retaining the state of each client's connection to Ably's frontend servers, allowing the server to continue receiving and storing messages on behalf of disconnected clients. This enables replaying of missed messages when a client reconnects. They have also addressed challenges related to resilient storage, connection state migration, fallback transports, and storing cursors instead of data for efficient message handling.