Migration Pattern — Problem

Pattern: Migration
Component: problem.md
Version: 1.2 | Updated: 2026-07-29

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Statement

Data or service moves ship as big-bang cuts: no dual-write/verify window, secrets in scripts, and irreversible drops without a rollback owner.

Measurable symptoms

Symptom	How you detect it
No return path	Rollback is “restore from backup someday”
Integrity surprises	Parity checks appear after cutover
Secret leakage	Connection strings in migration PRs
Digest drift	Unpinned images/jobs run “latest”

Root cause

Migrations look like engineering chores until they are irreversible. Speed bias deletes verify windows that are the only safe abort.

What breaks when this pattern is skipped

• Cutover war rooms become default
• Data class incidents during move
• Follow-up migrations to undo the last migration

Non-goals of this pattern

• Not a rewrite of product behavior (use Legacy Modernization)
• Not a license to skip security on “temporary” scripts
• Not MCP-driven DROP without a phase gate

Related

• Failures — recovery table
• Workflow — ordered steps
• Checklist — exit criteria

Changelog

• 1.2 (2026-07-29): Migration problem page expanded with skip-impact and operator symptoms.