# Salary Enhancement Deployment Strategy

## Overview

This document outlines the deployment strategy for the job salary enhancement feature, ensuring backward compatibility and zero-downtime deployment.

## Pre-Deployment Checklist

### Database Preparation
- [ ] Backup production database
- [ ] Test migration on staging environment
- [ ] Verify migration rollback procedure
- [ ] Confirm database user has necessary permissions

### Code Preparation
- [ ] All property-based tests passing
- [ ] Unit tests passing
- [ ] Integration tests passing
- [ ] Code review completed
- [ ] API documentation updated

### Infrastructure Preparation
- [ ] Staging environment matches production
- [ ] Monitoring alerts configured
- [ ] Rollback plan documented
- [ ] Team notification channels ready

## Deployment Steps

### Phase 1: Database Migration (Zero-Downtime)

1. **Apply Migration**
   ```bash
   npm run migration:run
   ```
   
2. **Verify Migration Success**
   ```bash
   npm run migration:show
   ```

3. **Validate Data Integrity**
   - Check existing jobs retain salaryRange data
   - Verify new columns are created with correct types
   - Confirm enum constraints are applied

### Phase 2: Application Deployment

1. **Deploy Backend Changes**
   - Deploy new API endpoints with salary fields
   - Maintain backward compatibility for mobile clients
   - Enable feature flags if available

2. **Verify API Functionality**
   - Test job creation with new salary fields
   - Test job retrieval with both old and new formats
   - Verify validation rules are working

### Phase 3: Mobile App Update

1. **Deploy Mobile Changes**
   - Update mobile app with new salary components
   - Ensure graceful handling of missing salary data
   - Test on various devices and OS versions

2. **Monitor User Experience**
   - Track API error rates
   - Monitor mobile app crash reports
   - Verify salary display formatting

## Backward Compatibility Strategy

### API Compatibility
- **Legacy Support**: Keep `salaryRange` field in responses for older mobile clients
- **Graceful Degradation**: New salary fields are optional, existing functionality preserved
- **Version Headers**: Use API versioning to manage different client expectations

### Data Migration Strategy
- **Preserve Legacy Data**: Existing `salaryRange` strings remain intact
- **Dual Format Support**: API returns both legacy and structured salary data
- **Gradual Migration**: New jobs use structured format, old jobs retain string format

### Mobile Client Compatibility
- **Progressive Enhancement**: New clients get enhanced salary features
- **Fallback Handling**: Older clients continue using `salaryRange` field
- **Feature Detection**: Mobile app detects available salary fields

## Rollback Procedures

### Database Rollback
```bash
# Revert migration if issues occur
npm run migration:revert
```

### Application Rollback
1. Deploy previous application version
2. Verify API functionality with reverted database
3. Monitor for any data inconsistencies

### Emergency Procedures
- **Immediate Issues**: Disable new salary features via feature flags
- **Data Corruption**: Restore from backup and replay safe transactions
- **Performance Issues**: Scale database resources or revert changes

## Monitoring and Validation

### Key Metrics to Monitor
- **API Response Times**: Ensure no performance degradation
- **Error Rates**: Monitor for validation or database errors
- **Mobile App Metrics**: Track crashes and user experience issues
- **Database Performance**: Monitor query performance and connection usage

### Validation Checkpoints
1. **Post-Migration**: Verify database schema changes
2. **Post-Deployment**: Test all salary-related API endpoints
3. **Post-Mobile Update**: Verify mobile app functionality
4. **24-Hour Check**: Monitor system stability and user feedback

## Success Criteria

### Technical Success
- [ ] Migration completes without errors
- [ ] All tests pass in production environment
- [ ] API response times remain within acceptable limits
- [ ] No increase in error rates

### Business Success
- [ ] Users can create jobs with structured salary data
- [ ] Job seekers see improved salary information display
- [ ] No disruption to existing job posting workflow
- [ ] Mobile app provides enhanced salary input experience

## Risk Mitigation

### High-Risk Scenarios
1. **Migration Failure**: Comprehensive testing and rollback procedures
2. **Data Loss**: Database backups and transaction logging
3. **Performance Impact**: Load testing and monitoring
4. **Mobile Compatibility**: Progressive deployment and feature flags

### Contingency Plans
- **Partial Rollback**: Ability to disable new features while keeping database changes
- **Data Recovery**: Procedures for restoring from backups if needed
- **Communication Plan**: User notification strategy for any service disruptions

## Post-Deployment Tasks

### Immediate (0-24 hours)
- [ ] Monitor system metrics and error logs
- [ ] Verify user feedback and support tickets
- [ ] Confirm mobile app store reviews remain positive
- [ ] Validate salary data accuracy in production

### Short-term (1-7 days)
- [ ] Analyze usage patterns of new salary features
- [ ] Gather user feedback on salary input experience
- [ ] Monitor database performance trends
- [ ] Plan any necessary optimizations

### Long-term (1-4 weeks)
- [ ] Evaluate feature adoption rates
- [ ] Consider removing legacy salaryRange field (future release)
- [ ] Document lessons learned
- [ ] Plan next phase of salary enhancements

## Contact Information

### Deployment Team
- **Database Administrator**: [Contact Info]
- **Backend Developer**: [Contact Info]  
- **Mobile Developer**: [Contact Info]
- **DevOps Engineer**: [Contact Info]

### Emergency Contacts
- **On-Call Engineer**: [Contact Info]
- **Product Manager**: [Contact Info]
- **Technical Lead**: [Contact Info]

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**Note**: This deployment strategy should be reviewed and approved by the technical team before execution. All team members should be familiar with rollback procedures before deployment begins.