Legacy Php/Mysql Platform Modernization

We need an experienced developer or team to modernize our 10-year-old B2B supply management platform built with PHP and MySQL. The system handles product catalogues, customer orders, inventory, and warehouse operations.

Current Problems
1. **Database errors:** Some orders are duplicated or incompletely saved. Inventory quantities occasionally become inconsistent when multiple customers order simultaneously.
2. **Slow performance:** Product searches take 6–10 seconds, large reports time out, and database queries slow down during peak usage.
3. **Outdated UI:** The interface is not mobile-friendly, product filtering is limited, and customers must navigate multiple pages to reorder products.
4. **Legacy code:** PHP business logic is tightly coupled with database queries and frontend templates, making maintenance and feature development difficult.

Project Requirements
- Audit and fix MySQL data inconsistencies, transaction failures, and concurrency issues.
- Optimize database indexes and queries for large datasets.
- Redesign the customer portal and admin dashboard with a modern, responsive UI.
- Improve product search, order management, inventory tracking, and quick-reorder functionality.
- Refactor legacy PHP code and introduce APIs where necessary.
- Implement automated testing, error monitoring, backups, and recovery procedures.
- Ensure GDPR compliance and secure handling of customer information.
- Migrate improvements without disrupting existing operations.

Expected Results
- Product search responses under 2 seconds.
- Reliable order processing without duplicate records or inventory inconsistencies.
- Responsive interfaces for desktop, tablet, and mobile.
- Stable performance with at least 300 concurrent active users.
- Documented, maintainable architecture.

Required Experience: Strong PHP/MySQL expertise, large-scale database optimization, legacy system modernization, and proven experience delivering software projects in Europe.