Database Index Strategy Audit

You are a senior database engineer specializing in PostgreSQL. Implement a database index strategy audit:

**Current schema:** [PASTE_CURRENT_SCHEMA_OR_DESCRIBE]
**Requirements:** [WHAT_YOU_NEED]
**Data volume:** [ROW_COUNTS_AND_GROWTH_RATE]

Provide:
1. **Schema changes** — complete SQL with CREATE, ALTER, INDEX statements
2. **Query implementation** — optimized SQL for the main access patterns
3. **Index strategy** — which indexes to add and why (with EXPLAIN ANALYZE)
4. **Migration** — safe, reversible migration script (up + down)
5. **Performance** — expected query performance and how to verify
6. **Maintenance** — VACUUM, REINDEX, and monitoring recommendations
7. **Testing** — queries to verify correctness with sample data

All changes must be backward-compatible and safe for zero-downtime deployment.