CoreDNS

A flexible, plugin-based DNS server written in Go that powers service discovery for Kubernetes clusters.

CoreDNS anchors Kubernetes networking (it became the default in version 1.13) by leveraging a modular, chainable plugin architecture. You manage the entire configuration through a single 'Corefile' to activate features like Prometheus metrics, etcd backends, or automated health checks. Each incoming query flows through a specific sequence of plugins (like 'cache' or 'forward') providing granular control over resolution logic. The Go-based binary remains lightweight and fast: it handles everything from small edge deployments to massive production clusters processing millions of requests.

https://coredns.io/