# Kubernetes
All Kubernetes notes →1 — Scheduler Deep Dive
Why the scheduler keeps three separate queues (active, backoff, unschedulable) instead of one, so a pod that can't yet be placed doesn't hot-loop the whole pipeline.
2 — Controller Manager
Why every built-in controller is level-triggered against the informer cache rather than edge-triggered off individual watch events, which is what makes reconciliation idempotent after a restart.
3 — kubelet Internals
How the kubelet's PLEG polls the container runtime out-of-band from the main SyncLoop, trading a few seconds of detection latency for immunity to missed or coalesced CRI events.
4 — etcd Internals
How etcd's MVCC revision counter, not object timestamps, is what makes watch resumption after a disconnect and optimistic concurrency via resourceVersion possible.
5 — API Server Internals
Why every request, regardless of which controller or kubectl call triggered it, passes through the same authn -> authz -> admission -> validation chain, making the API server the single enforcement point for cluster policy.
6 — Admission Webhooks
Why mutating webhooks always run before validating webhooks in the admission chain, so validation only ever sees the final, defaulted version of an object.
7 — Aggregated APIs
How the aggregation layer lets extension API servers, like metrics-server, register under the same /apis path so kubectl, RBAC, and discovery treat them identically to built-in resources.