Full stack developer - B2B Marketplace Platform

I'm looking for an experienced Full-Stack Developer or a small development agency with proven experience building scalable SaaS platforms or online marketplaces. Please only apply if you have built similar systems and can provide live examples. Core functionality 1. Employee Portal Secure login Browse thousands of classes and experiences Search and filter by activity, location, date, provider, and category Book experiences Cancel bookings according to provider rules View booking history View upcoming bookings View remaining wellness allowance Save favorites Email notifications and reminders 2. Employer Dashboard Secure login Manage employees Bulk employee import (CSV/Excel) Allocate wellness budgets Monitor employee engagement Live analytics dashboard Budget tracking Reports and exports Invoice management 3. Provider Dashboard Secure login Create and edit activities Upload photos and descriptions Manage schedules and availability Set participant capacity Confirm or decline bookings View upcoming bookings Revenue dashboard Invoice downloads 4. Platform Admin Manage employers Manage providers Manage employees Manage bookings Manage categories Analytics Content management Promotional campaigns Commission management Reporting Technical Requirements The platform should be scalable and support: Thousands of employers Tens of thousands of employees Thousands of providers Thousands of experiences and classes Preferred technologies (open to recommendations): React or Next.js Node.js (NestJS or Express) PostgreSQL REST or GraphQL APIs Stripe integration Docker AWS, Azure, or Google Cloud Important requirements: Strong security GDPR compliance Responsive design Clean architecture High performance Future mobile app compatibility Multilingual support (English, French, German, Luxembourgish) Please include in your proposal Examples of SaaS or marketplace platforms you have built. Your recommended technology stack and why. How you would architect this platform for scalability. An estimated timeline for delivering an MVP. Your estimated budget range. I am looking for a long-term development partner rather than someone who will simply build a website. The goal is to create a robust, scalable platform that can grow across European countries.