# Kubernetes
All Kubernetes notes →1 — Scheduler Internals
Why the scheduler's filter-then-score two-phase pipeline exists instead of just placing a pod on the first node that fits.
10 — Upgrades & Version Skew
Why the N-2 kubelet-to-API-server version skew policy is what lets a large fleet upgrade gradually instead of needing a synchronized all-at-once cutover.
2 — nodeSelector
Why nodeSelector's exact-match label equality makes it too blunt for anything beyond simple hardware-tier pinning.
3 — Node Affinity
Why splitting node affinity into required (hard) and preferred (soft) rules lets you express 'must have SSD' and 'prefer us-east' in the same spec.
4 — Pod Affinity & Anti-Affinity
Why the topology key, not just 'same node' or 'different node', is what actually spreads replicas across real failure domains.
5 — Taints & Tolerations
Why taints repel pods by default while tolerations only grant permission to land there — they never force placement the way affinity does.
6 — Priority Classes
Why priority classes only matter at eviction and preemption time under resource pressure, not as a routine scheduling hint.
7 — Topology Spread Constraints
Why maxSkew is the one knob that finally balances replicas evenly across zones without the all-or-nothing rigidity of anti-affinity.
8 — Node Maintenance
Why cordon-then-drain, not a bare delete, is the only sequence that respects PodDisruptionBudgets while evacuating a node.
9 — Cluster Lifecycle
Why control-plane and etcd lifecycle, not just worker node churn, is the part of 'cluster lifecycle' most operators under-plan for.
# Operating System
All Operating System notes →1 — Scheduling Fundamentals
Covers scheduling goals: throughput, turnaround time, waiting time, response time, and fairness.
2 — Scheduling Algorithms
Covers FCFS, SJF, SRTF, round robin, priority scheduling, multilevel queue scheduling, MLFQ, and lottery scheduling.
3 — Modern Scheduler Design
Covers the Linux Completely Fair Scheduler (CFS), the Windows scheduler, CPU affinity, load balancing, and NUMA-aware scheduling.