Refactor Safely

1. Dead code removal — find unreferenced functions, unused imports, orphaned files
2. Extract service — if a file > 300 lines, split by responsibility
3. Type consolidation — if same shape defined in multiple places, create shared type
4. Error handling — replace try/catch with structured error types
5. Performance — identify N+1 queries, missing indexes, redundant DB calls

Impact Assessment

Before applying any refactor:

• List ALL files that import from the changed module
• Check if any worker depends on the changed code (workers run separately)
• Check if the SDK (@sendmesh/node) wraps the affected endpoint
• Check if documentation references the affected API/types
• Estimate blast radius: 1-3 files (safe), 4-10 (review), 10+ (pause, design doc first)

Post-Refactor Verification

1. npx tsc --noEmit — zero type errors
2. npm run test — all pass
3. npm run build — succeeds
4. Verify API responses match OpenAPI spec
5. Verify queue processing still works (send test email end-to-end)