Cluster DNS

The in-cluster resolver that maps service names to virtual addresses, making service-to-service calls a hostname rather than a discovery problem. It is a hard dependency of nearly every request path, so a saturated or crash-looping DNS deployment presents as intermittent failures everywhere at once rather than as a DNS incident. Aggressive search-domain expansion also means one lookup can become five queries, which is why DNS is a surprisingly common source of tail latency.