We actually recommend applying the first rule to all clusters, as suggested in the Introducing indirection recipe. It's especially important here as the focus is specifically centered on maximizing availability.
Unlike a standard PostgreSQL node, a cluster containing multiple primary nodes does not require the promotion of alternate systems to writable status. This means we can switch to them in a nearly instantaneous manner. A properly configured proxy layer means this is possible without directly alerting the application layer. Such a cluster could resemble this diagram:
Given this configuration, it's possible to switch from ...
