Data integrity in Ably Pub/Sub

The Ably Pub/Sub architecture ensures reliable and efficient message delivery across a global network of servers, with a focus on data integrity. Each region in Ably can operate independently but also coordinates with other regions to share and replicate messages globally. Messages are processed and stored by primary locations before being acknowledged, while secondary locations store backup copies. In case of regional failures, the system ensures seamless fallback to another region without affecting global availability. The architecture supports exactly-once delivery through idempotent publishing and message delivery on SDKs, ensuring no duplicates or gaps in the message stream. Additionally, messages maintain their order relative to other messages on the same WebSocket connection, providing causal consistency for each client. Overall, Ably's Pub/Sub system is designed to "just work" with a focus on data integrity and performance.