---
id: "AE22-013"
category: "infrastructure"
confidence: 0.98
date: "2026-02-15"
source_file: "PRODUCTION_HARDENING_PLAN.md (Section 2.4 Zero-Downtime Migration Rules)"
---

# AE22-013

Zero-downtime database migrations require 4 rules: never drop columns in same release that removes code, always ADD columns as nullable first then backfill, always use CREATE INDEX CONCURRENTLY, and use two-phase column removal (Release 1: stop using, Release 2: drop)
