I'm thrilled to have people digging into this, because I think it's a super interesting problem, but: no, keeping quorum nodes close-enough-but-not-too-close doesn't solve our problem, because we support a unified customer namespace that runs from Tokyo to Sydney to São Paulo to Northern Virginia to London to Frankfurt to Johannesburg.
Two other details that are super important here:
This is a public cloud. There is no real correlation between apps/regions and clients. Clients are public Internet users. When you bring an app up, it just needs to work, for completely random browsers on completely random continents. Users can and do move their instances (or, more likely, reallocate instances) between regions with no notice.
The second detail is that no matter what DX compromise you make to scale global consensus up, you still need reliable realtime update of instances going down. Not knowing about a new instance that just came up isn't that big a deal! You just get less optimal routing for the request. Not knowing that an instance went down is a very big deal: you end up routing requests to dead instances.
The deployment strategy you're describing is in fact what we used to do! We had a Consul cluster in North America and ran the global network off it.
Two other details that are super important here:
This is a public cloud. There is no real correlation between apps/regions and clients. Clients are public Internet users. When you bring an app up, it just needs to work, for completely random browsers on completely random continents. Users can and do move their instances (or, more likely, reallocate instances) between regions with no notice.
The second detail is that no matter what DX compromise you make to scale global consensus up, you still need reliable realtime update of instances going down. Not knowing about a new instance that just came up isn't that big a deal! You just get less optimal routing for the request. Not knowing that an instance went down is a very big deal: you end up routing requests to dead instances.
The deployment strategy you're describing is in fact what we used to do! We had a Consul cluster in North America and ran the global network off it.