Add cache-hit-specific duration metric (contrast with cache_resolution) #682

The existing duration metric can't easily be filtered to show only cache hits, making it hard to contrast hit vs. miss performance against cache_resolution.

Ask

Either:

1. Add a cache_hit_duration metric that captures latency for requests served from cache, OR
2. Add a cache_hit label/dimension to the existing duration metric so it can be filtered in Grafana.

The goal is to be able to show: "cache hit latency = X ms vs. cache miss latency = Y ms" in a dashboard.

If there's already a way to compute this with existing metrics, documentation would be equally valuable.

🤖 Filed by Claude on behalf of Kris.