One service pointed its cache at a hostname that never existed

A service was configured to reach its cache at a -redis-master address. No such address has ever existed in that namespace - the operator names the service -redis.

The name never resolved, so the service ran without a working cache for its entire life. Nothing alerted: the application degrades quietly when the cache is unreachable, and the cache instance itself was healthy, just idle. It held zero keys, which is what led to the discovery.

Fixed on 2026-08-19 while enabling authentication across the caching layer. The service is now using its cache for the first time.

Worth noting as a pattern: an idle cache holding zero keys is a signal worth checking, not a quiet success.