Persistence Layer Change

Skill: backend/persistence-layer-change

Purpose

Change persistence safely by managing:

• schema changes (tables/columns/indexes)
• migrations
• updated read/write paths
• compatibility and rollout strategy

This skill is responsible for preventing data loss and breaking changes.

Inputs

• Desired schema change (add/alter/remove)
• Backward compatibility needs:
  • can deploy in one step or requires multi-step rollout
• Data access layers involved (ORM/query builder/raw SQL)
• Repo profile (preferred): <repo>/REPO_PROFILE.json

Outputs

• Migration(s) or schema change artifact(s)
• Updated data access code to use new schema
• Tests updated or added
• Notes on rollout if multi-step needed (in comments or docs if repo standard)

Non-goals

• Business logic changes unrelated to the schema
• Endpoint wiring (unless required for compilation)
• Rewriting the persistence layer wholesale

Workflow

1. Identify existing migration mechanism and conventions.
2. Choose safe change strategy:
   • additive change first (preferred)
   • dual-write or backfill if required
   • destructive change only with explicit migration plan
3. Implement migration with deterministic up/down behavior when supported.
4. Update data access paths:
   • reads tolerate both states during rollout if needed
   • writes remain consistent
5. Add/adjust indexes carefully (avoid accidental perf regressions).
6. Add tests:
   • migration applies
   • reads/writes work
7. Run required validations from profile.

Checks

• Migration applies cleanly in a fresh environment (as supported by repo)
• No destructive change without explicit plan
• Tests pass (and cover at least one new access path)
• Typecheck/lint pass if configured
• Performance hazards considered (indexes, N+1, full scans)

Failure modes

• Migration framework missing → stop and recommend establishing it before change.
• Destructive change requested → require staged plan and rollback notes.
• Unknown production constraints → recommend conservative additive migration first.

Telemetry

Log:

• skill: backend/persistence-layer-change
• migration_type: additive | staged | destructive
• artifacts_written: migration file(s)
• files_touched
• outcome: success | partial | blocked