Not directly related (and a bit of a random asidre), but I've always found linkerd's (actually finagle's) dtab routing rules quite intriguing, and possibly a good way of decoupling "fleets" of services. Was thinking in the past about implementing something similar as a dsl in kotlin to plug into http4k, but never yet found the use case to drive it:
https://linkerd.io/1/advanced/dtabs/