Chat. A messenger for teams

A team chat in Europe and the USA: delivering events through gateways, a service in two regions with one write leader, message order, and what is lost when a region goes down.

Diagram of a team chat: gateways in two regions keep connections to clients, messages flow in order, and one write leader’s database feeds the other.

System Design — Load balancers, caches, queues and regions: build a system that holds the load