A few years into running a JVM backend in production, I stopped trusting dashboards just because they were green. The numbers weren't wrong, exactly — CPU fine, heap fine, request count nominal — but "green dashboard, angry customer" kept happening often enough that I started keeping a private list of incidents where every chart we had swore everything was fine. It was always the same story: we were watching the machine, not the request. A service can sit comfortably under every resource limit i...