Migration Planning for Magento 2

Pre-Migration Audit

Code Assessment

# Module compatibility check
php bin/magento module:status

# Custom code inventory
find app/code/Vendor -name '*.php' | wc -l

# Deprecated API usage
rg '@deprecated|@see.*deprecated' app/code/ --include='*.php'

# Third-party module inventory
composer show | grep -i 'magento-'

Assessment Checklist

Custom Modules:
- [ ] List all custom modules
- [ ] Check Magento version compatibility
- [ ] Identify deprecated API usage
- [ ] Assess test coverage per module
- [ ] Document module dependencies

Third-Party Modules:
- [ ] List all marketplace modules
- [ ] Verify version compatibility
- [ ] Check for replacement modules
- [ ] Assess vendor support status

Data Assessment:
- [ ] Database size and growth rate
- [ ] Custom tables and their purposes
- [ ] Data volume per entity
- [ ] Media file count and size

Infrastructure:
- [ ] Current server specifications
- [ ] PHP/MySQL/Elasticsearch versions
- [ ] Cache configuration
- [ ] CDN and WAF setup

Effort Estimation

// Example estimation model
$effort = [
    'custom_modules' => count($customModules) * 8,  // hours per module
    'third_party' => count($thirdParty) * 16,        // hours per module
    'data_migration' => 40,                          // base hours
    'testing' => $totalHours * 0.3,                  // 30% for testing
    'deployment' => 24,                              // hours
];

Phase-Based Approach

Phase 1: Preparation (2-4 weeks)

Objectives:
- Complete assessment
- Set up target environment
- Create migration branch
- Establish testing infrastructure

Deliverables:
- Migration plan document
- Risk register
- Test plan
- Rollback procedures

Phase 2: Foundation (4-8 weeks)

Objectives:
- Upgrade core Magento
- Update PHP/MySQL versions
- Install compatible third-party modules
- Fix critical compatibility issues

Deliverables:
- Working base installation
- Unit test suite passing
- Basic smoke tests passing

Phase 3: Module Migration (8-16 weeks)

Objectives:
- Migrate custom modules one by one
- Update deprecated API usage
- Add/update tests per module
- Verify functionality

Deliverables:
- All custom modules migrated
- Test coverage maintained/increased
- Documentation updated

Phase 4: Data Migration (2-4 weeks)

Objectives:
- Migrate data with Data Migration Tool
- Validate data integrity
- Migrate media files
- Verify order/customer/product data

Deliverables:
- Complete data in target system
- Data validation report
- Performance benchmarks

Phase 5: Testing & Deployment (2-4 weeks)

Objectives:
- End-to-end testing
- Performance testing
- Security audit
- Production deployment

Deliverables:
- UAT sign-off
- Performance report
- Go-live checklist
- Post-launch monitoring

Timeline Visualization

Week:  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16
Phase: |--P1--|-----P2-----|----------P3----------|--P4--|--P5--|

Milestone Criteria

M1 - Assessment Complete: All modules cataloged, risks identified
M2 - Foundation Ready: Core upgraded, basic tests passing
M3 - Module Migration Done: All custom modules working
M4 - Data Migrated: All data validated and accessible
M5 - Go-Live: Production deployment successful

Common Migration Risks

Risk Register Template

| Risk ID | Description | Probability | Impact | Mitigation | Owner |
|---------|-------------|-------------|--------|------------|-------|
| R1 | Third-party module incompatible | High | High | Contact vendor, find alternative | Dev Lead |
| R2 | Data corruption during migration | Low | Critical | Multiple backups, validation scripts | DBA |
| R3 | Performance regression | Medium | High | Benchmark before/after, load testing | DevOps |
| R4 | Extended downtime | Medium | High | Blue-green deployment, staged rollout | DevOps |
| R5 | Custom code breaks | High | Medium | Comprehensive testing, rollback plan | Dev Lead |

Risk Mitigation Strategies

Data Loss Prevention

# Before migration
mysqldump -u root -p magento_backup_$(date +%Y%m%d)

# During migration
php bin/magento setup:rollback --backup-file=...

# Validation script
php bin/magento data:migration:validate

Downtime Minimization

Strategies:
1. Blue-green deployment
2. Database replication
3. Staged feature rollout
4. Maintenance window scheduling
5. CDN caching of static assets

Rollback Planning

Rollback Trigger:
- Critical functionality broken
- Data integrity issues
- Performance degradation > 30%
- Security vulnerability introduced

Rollback Steps:
1. Stop traffic to new system
2. Restore database from backup
3. Switch DNS to old environment
4. Verify old system functionality
5. Communicate to stakeholders
6. Analyze failure cause
7. Plan corrective action

Contingency Plans

Scenario: Module vendor doesn't support new version
Response: Fork module, implement fix, schedule replacement

Scenario: Data migration fails halfway
Response: Restore from backup, fix migration script, retry

Scenario: Performance severely degraded
Response: Scale up infrastructure, optimize queries, enable additional caching

Scenario: Critical bug found post-launch
Response: Hotfix deployment, feature flag disable, rollback if needed

Stakeholder Communication

Status Report Template

## Migration Status Report - [Date]

### Progress
- Phase: 3 of 5 (Module Migration)
- Completed: 8 of 12 custom modules
- On Track: Yes

### Blockers
- Module X requires PHP 8.2, waiting for vendor update

### Risks Updated
- R3 (Performance): Mitigated with new caching strategy

### Next Steps
- Complete remaining 4 modules
- Begin data migration planning

### Metrics
- Test Coverage: 72% → 78%
- PHPStan Errors: 47 → 23

Go-Live Checklist

Pre-Launch:
- [ ] All tests passing
- [ ] Performance benchmarks met
- [ ] Security scan clean
- [ ] Backups verified
- [ ] Rollback procedure tested
- [ ] DNS TTL reduced
- [ ] Monitoring configured
- [ ] Support team notified

Launch:
- [ ] Deploy to production
- [ ] Run data migration
- [ ] Verify critical paths
- [ ] Monitor error rates
- [ ] Check performance metrics

Post-Launch:
- [ ] Monitor for 24-48 hours
- [ ] Address any issues
- [ ] Decommission old system (after 2 weeks)
- [ ] Document lessons learned

Monitoring During Migration

Key Metrics:
- Error rate (target: < 0.1%)
- Page load time (target: < 3s)
- Conversion rate (compare to baseline)
- Server resource utilization
- Database query performance

Alerting:
- Error spike > 1% → immediate investigation
- Response time > 5s → scale/rollback
- Memory > 80% → investigate/kill processes