Active/Active Multi-region - Chat application Architecture

In the previous post I covered how I connected two Kubernetes clusters across Mongolia and Germany using Netbird. That was the networking layer — pods can reach each other, DNS works across clusters. Now the interesting part: making the actual application work active/active across both regions. Active/active means both clusters run independently and serve users, but a user on cluster A can chat with a user on cluster B in real time. No single point of failure, no "primary" region. Either cluster