The benefits of serving stale DNS entries when using Consul

What this post added

This post details the implementation and testing of Unbound's `serve-expired` feature to improve DNS resolution latency and resilience when using Consul for service discovery. It covers the configuration of `serve-expired`, `serve-expired-ttl`, and `serve-expired-client-timeout`, and demonstrates successful testing scenarios for serving stale records indefinitely, handling negative/incomplete information, and background cache refreshing. It also notes an upstream fix for prefetching logic blocking stale cache serving.