Optimize this slow database query

Fix the N+1 query problem in this code

Analyze query performance and suggest indexes

# Bad: N+1 queries
users = User.all()
for user in users:
    posts = Post.where(user_id=user.id)  # N queries

# Good: Single query with JOIN
users = User.all().includes(:posts)  # 1 query

## Database Optimization: User Query

### Current Query
```sql
SELECT * FROM users
WHERE email = 'user@example.com';
-- Execution time: 450ms

-- Add index
CREATE INDEX idx_users_email ON users(email);

-- Optimized query
SELECT id, email, name FROM users
WHERE email = 'user@example.com';
-- Execution time: 2ms

## Best Practices

### Database Optimization

1. **Measure First**: Use EXPLAIN ANALYZE
2. **Index Strategically**: Not every column needs an index
3. **Monitor**: Track slow query logs
4. **Cache**: Cache expensive queries
5. **Denormalize**: When justified by read patterns

## Reference Files

- **`references/query_patterns.md`** - Common query optimization patterns, anti-patterns, and caching strategies

## Related Use Cases

- Query optimization
- Index design
- N+1 problem resolution
- Caching implementation
- Database performance improvement