261 lines
7.0 KiB
Markdown
261 lines
7.0 KiB
Markdown
# MongoDB to MySQL Migration Summary
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## Overview
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This document has been successfully migrated from **MongoDB/Mongoose** to **MySQL/Sequelize** architecture.
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---
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## Major Changes
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### 1. **Technology Stack Update**
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- **Changed from**: MongoDB with Mongoose ODM
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- **Changed to**: MySQL 8.0+ with Sequelize ORM
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- **Stack name**: Updated from "MEAN Stack" to "MySQL + Express + Angular + Node"
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### 2. **Database Schema Transformation**
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#### ID Strategy
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- **MongoDB**: ObjectId (12-byte identifier)
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- **MySQL**: UUID (CHAR(36) or BINARY(16))
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#### Data Types Mapping
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| MongoDB | MySQL |
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|---------|-------|
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| ObjectId | CHAR(36) UUID |
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| String | VARCHAR/TEXT |
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| Number | INT/DECIMAL |
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| Boolean | BOOLEAN |
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| Date | TIMESTAMP |
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| Mixed | JSON |
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| Array | JSON or Junction Tables |
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| Embedded Documents | JSON or Separate Tables |
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#### Schema Design Approach
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- **Normalized tables** for core entities (users, questions, categories)
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- **Junction tables** for many-to-many relationships (bookmarks, achievements, quiz questions)
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- **JSON columns** for flexible data (question options, keywords, tags, feature restrictions)
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- **Proper foreign keys** with cascading deletes/updates
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### 3. **Database Tables Created**
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1. **users** - User accounts and statistics
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2. **categories** - Question categories
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3. **questions** - Question bank with guest visibility controls
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4. **quiz_sessions** - Active and completed quiz sessions
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5. **quiz_session_questions** - Junction table for session questions
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6. **quiz_answers** - Individual question answers
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7. **guest_sessions** - Guest user sessions
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8. **guest_settings** - Guest access configuration
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9. **guest_settings_categories** - Junction table for guest-accessible categories
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10. **achievements** - Achievement definitions
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11. **user_achievements** - User earned achievements
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12. **user_bookmarks** - User bookmarked questions
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### 4. **Key Features**
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#### Indexes Added
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- Primary key indexes (UUID)
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- Foreign key indexes for relationships
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- Composite indexes for common queries
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- Full-text search indexes on question content
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- Performance indexes on frequently queried columns
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#### MySQL-Specific Optimizations
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- InnoDB storage engine
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- UTF8MB4 character set for emoji support
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- Connection pooling configuration
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- Query optimization examples
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- Backup and restore strategies
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### 5. **Sequelize Models**
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All models include:
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- UUID primary keys
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- Proper associations (hasMany, belongsTo, belongsToMany)
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- Field name mapping (camelCase to snake_case)
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- Timestamps (created_at, updated_at)
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- Validation rules
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- Indexes defined at model level
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### 6. **Configuration Updates**
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#### Environment Variables
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```bash
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# Old (MongoDB)
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MONGODB_URI=mongodb://localhost:27017/interview_quiz
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# New (MySQL)
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DB_HOST=localhost
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DB_PORT=3306
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DB_NAME=interview_quiz_db
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DB_USER=root
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DB_PASSWORD=your_password
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DB_DIALECT=mysql
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```
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#### Dependencies to Update
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```bash
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# Remove
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npm uninstall mongoose
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# Install
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npm install sequelize mysql2
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npm install -g sequelize-cli
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```
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### 7. **Migration Strategy**
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#### Development Setup
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1. Install MySQL 8.0+
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2. Create database with UTF8MB4
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3. Run Sequelize migrations
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4. Seed initial data
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5. Start application
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#### Migration Commands
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```bash
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# Initialize Sequelize
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npx sequelize-cli init
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# Create migration
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npx sequelize-cli migration:generate --name migration-name
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# Run migrations
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npx sequelize-cli db:migrate
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# Rollback migration
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npx sequelize-cli db:migrate:undo
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# Seed database
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npx sequelize-cli db:seed:all
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```
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### 8. **Security Enhancements**
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- **SQL Injection Prevention**: Sequelize parameterized queries
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- **Prepared Statements**: All queries use prepared statements
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- **Connection Security**: SSL/TLS support for production
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- **Role-based Access**: Maintained through user roles table
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### 9. **Performance Considerations**
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#### Query Optimization
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- Use of composite indexes
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- Efficient JOIN operations
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- Connection pooling (max 10 connections)
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- Query result caching with Redis
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- Lazy loading for associations
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#### Database Configuration
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- InnoDB buffer pool tuning
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- Query cache optimization (MySQL 5.7)
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- Binary logging for replication
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- Slow query log monitoring
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### 10. **Deployment Updates**
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#### Development
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- Local MySQL instance
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- Sequelize migrations for schema management
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#### Staging
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- Managed MySQL (AWS RDS, Azure Database, PlanetScale)
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- Automated migration deployment
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#### Production
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- Read replicas for scaling
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- Automated backups (daily snapshots)
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- Point-in-time recovery
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- Connection pooling with ProxySQL (optional)
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---
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## What Stayed the Same
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✅ **API Endpoints** - All endpoints remain unchanged
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✅ **Frontend Code** - No changes required to Angular app
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✅ **JWT Authentication** - Token strategy unchanged
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✅ **Business Logic** - Core features remain identical
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✅ **User Stories** - All acceptance criteria maintained
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---
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## Breaking Changes
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⚠️ **Database Migration Required** - Cannot directly migrate MongoDB data to MySQL without transformation
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⚠️ **ORM Changes** - All Mongoose code must be rewritten to Sequelize
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⚠️ **Array Queries** - MongoDB array operations need to be rewritten for JSON columns or junction tables
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⚠️ **Aggregation Pipelines** - Complex MongoDB aggregations need to be rewritten as SQL JOINs and GROUP BY
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---
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## Data Migration Steps
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If migrating existing MongoDB data:
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1. **Export MongoDB Data**
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```bash
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mongoexport --db interview_quiz --collection users --out users.json
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mongoexport --db interview_quiz --collection questions --out questions.json
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# ... export all collections
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```
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2. **Transform Data**
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- Convert ObjectIds to UUIDs
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- Flatten embedded documents
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- Split arrays into junction tables
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- Map MongoDB types to MySQL types
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3. **Import to MySQL**
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```bash
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# Use custom Node.js script to import transformed data
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node scripts/import-from-mongodb.js
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```
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---
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## Testing Checklist
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- [ ] All database tables created successfully
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- [ ] Foreign key constraints working
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- [ ] Indexes created and optimized
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- [ ] User registration and login working
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- [ ] Guest session management working
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- [ ] Quiz session creation and completion
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- [ ] Question CRUD operations (admin)
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- [ ] Bookmark functionality
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- [ ] Achievement system
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- [ ] Full-text search on questions
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- [ ] Dashboard statistics queries
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- [ ] Performance testing (1000+ concurrent users)
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- [ ] Backup and restore procedures
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- [ ] Migration rollback testing
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---
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## Additional Resources
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### Sequelize Documentation
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- [Sequelize Official Docs](https://sequelize.org/docs/v6/)
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- [Migrations Guide](https://sequelize.org/docs/v6/other-topics/migrations/)
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- [Associations](https://sequelize.org/docs/v6/core-concepts/assocs/)
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### MySQL Documentation
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- [MySQL 8.0 Reference](https://dev.mysql.com/doc/refman/8.0/en/)
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- [InnoDB Storage Engine](https://dev.mysql.com/doc/refman/8.0/en/innodb-storage-engine.html)
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- [Performance Tuning](https://dev.mysql.com/doc/refman/8.0/en/optimization.html)
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---
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## Version Information
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- **Document Version**: 2.0 - MySQL Edition
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- **Migration Date**: November 2025
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- **Database**: MySQL 8.0+
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- **ORM**: Sequelize 6.x
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- **Node.js**: 18+
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---
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**Migration completed successfully!** 🎉
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