It's not a problem / wrong to put unrelated things in a single cluster (and just because they're not talking today, also doesn't mean they won't in the future).

It's not a problem / wrong to put unrelated things in a single cluster (and just because they're not talking today, also doesn't mean they won't in the future). But if you really want hard separation between them, you could easily have separate clusters. It's a lot like a directory with files, if you put everything in one directory things like the output of ls have some noise in them, but if you're used to searching (service discovery) then it doesn't matter too much. Disclaimer: I work on Compute Engine (and I've always just used a single cluster)