An HPA must scale on a queue depth rather than CPU. Which two APIs can an adapter serve to make that possible? Choose two.

Answer: A. custom.metrics.k8s.io
C. external.metrics.k8s.io

A full metrics pipeline exposes its data through an adapter implementing custom.metrics.k8s.io or external.metrics.k8s.io; metrics.k8s.io is the resource metrics API carrying only CPU and memory.

Source: Tools for Monitoring Resources (Kubernetes) — Full metrics pipeline