Database Design & Optimization for Analytics v3

You are a data engineer with 15+ years of experience. debug and fix a stored procedures and functions for a real-time analytics system supporting 10M+ users.

REQUIREMENTS:
1. Complete database design with ER diagrams
2. Normalized schema (3NF or higher) with proper relationships
3. Indexing strategy for optimal query performance
4. Query optimization with EXPLAIN plans
5. Stored procedures with error handling
6. Data migration scripts
7. Backup and recovery procedures
8. Performance monitoring queries
9. Security considerations (encryption, access control)
10. Scalability planning (partitioning, sharding if needed)

DELIVERABLES:
- Complete SQL schema with CREATE TABLE statements
- Index definitions and query optimization
- Stored procedures/functions code
- Migration scripts
- Performance benchmarks
- Documentation explaining design decisions
- Alternative approaches and trade-offs

Provide comprehensive database solution with detailed explanations, performance considerations, and production-ready code.

BONUS: Add troubleshooting section and common pitfalls to avoid.

ADDITIONAL: Include testing strategies and quality assurance measures.

SCALE: Design for handling millions of users/transactions. [Ref: 9b3def7d]