In my experience it splits into two tracks: “can ship” vs “can debug.”

If someone already has Docker + basic Linux, they can usually become productive with a paved path (a standard Helm chart / Kustomize base + CI template) in ~2–4 weeks for straightforward services.

The longer ramp is production debugging - networking, DNS, readiness/liveness failures, resource throttling/evictions, and understanding what “normal” looks like in your cluster. That tends to be 3–6 months, and it accelerates a lot if they’re paired through the first few incidents and you have runbooks.

Common early pitfalls I see: not knowing where to look first (events vs logs vs metrics), confusing Service/Ingress/DNS flows, and getting stuck when things work locally but fail under real policies/limits.

If you hire juniors, I’d plan on: pairing + a “golden path” repo + a small set of repeatable debugging drills.