Full-Stack Geospatial & FinTech Developer

We are seeking a senior, independent Full-Stack Geospatial Software Engineer to build the foundational backend, website and mobile architecture for an urban infrastructure utility platform. The project requires a decoupled, API-driven architecture separating a secure spatial database from distinct consumer modules, including geographic addressing, artisan marketplace, and real estate escrows which can also handle public private partnership splits. Core deliverables include designing a PostgreSQL/PostGIS database optimized for 90,000+ structure records for multiple urban areas?towns, building a Flutter mobile app possibly for RTK GNSS data capture, and implementing secure REST API webhooks for regional payment gateway integration. The ideal freelancer should be able to lead multi-phase infrastructure development with strong security and scalability considerations.