Istio failures often occur while pods, Services, and Deployments are perfectly healthy. A route mismatch, missing destination subset, or conflicting policy can break traffic at the Envoy layer, and normal Kubernetes checks will not catch it.
Without following this practice, teams typically discover the problem during a production incident. The cost of fixing issues reactively is 10-100x higher than preventing them proactively. This becomes especially dangerous at scale when multiple teams depend on the same infrastructure, because one team's shortcut becomes another team's outage. Organizations that skip this practice often find themselves in a cycle of firefighting instead of building. The pattern is predictable: it works fine in development, survives staging, and fails spectacularly in production under real traffic and real failure conditions.
