Building a multi-region routing system with Cloudflare Workers

We serve customers primarily in Australia, but we are now expanding to the USA. The timeline for launch is less than 2 months. This is now a race against time to design a multi-region routing system that fits all of our needs. Here is the story. Background Almost all of our customers were based in Oceania. We run our Kubernetes Cluster on GCP in Australia. Go microservices, federated GraphQL, gRPC services. 2 products - Tutoring and Schools. All designed for Australia. Then we expanded to the USA, which meant a new Kubernetes Cluster in US Central. The latency for serving US customers from Australia is an extra 200ms-300ms depending on network conditions - unacceptable. This would mean sharding the data by region, or does it? There are definitely ways to keep a unified dataset even across regions - though we did not need to do so. More on this later. What are the requirements If the only requirements were "Americans get served from America", we wouldn't be here discussing this, would we? Logged in users are served from their own region, wherever they happen to be in the world. Logged out users are routed geographically, as we have no other information to infer their actual region. Account Managers and Admins should be able to access both regions from one button, with a single account. Teaching materials opened via links from the Schools product must be shareable across both regions. Geography takes care of the logged out user, but nothing else. Using geography for a logged in user can be actively wrong. They might be travelling or simply using a VPN. Then comes the Admin; we have a lot of admin operations regarding curricula, which will be entirely separate for both clusters. Account Managers need to be able to see and modify information on both clusters. One admin should be able to access both clusters with a single account. We considered showing data of both clusters on one screen, but ruled it out as it may become too ambiguous or confusing, not worth the technic