# Availability levels and derived pod spread

{/* Stub. Why one failure-scope vocabulary (none | pod | node | zone) instead of per-package HA switches, why it is derived from the substrate and capped by it, and why spread and PDBs are compiled in rather than written by each package. Source: v2_discussions/archive/145_availability_level.md and archive/143_pod_spread_and_failure_zones.md. */}