Senior Full-Stack Developer for B2B SaaS Construction Compliance Platform

We are looking for an experienced Senior Full-Stack Developer to build a production-ready, multi-tenant B2B SaaS platform for managing construction permit conditions and compliance tasks. The platform will be used by construction companies to create projects, upload permit decisions, manage individual conditions, assign responsibilities, collaborate with specialist planners, store documents and comments, track progress, and prepare reports. Initial workflow For the first version, the extraction of conditions from permit documents will be handled manually: A customer creates a new project. The customer uploads the construction permit decision as a PDF. The document appears in an internal admin inbox. We manually enter the relevant conditions into a standardized Excel template. The Excel file is uploaded to the platform. The system validates the file and automatically creates the project’s conditions table. The customer and assigned specialists can then work with the conditions inside the platform. The architecture must be designed so that the manual extraction process can later be replaced or supplemented by an AI/OCR-based extraction service without rebuilding the core platform. Main deliverables The first commercial version should include: Multi-tenant SaaS architecture Secure authentication and role-based permissions Roles for SaaS administrator, project manager, specialist planner, and viewer Customer and project management PDF upload and document storage Internal admin inbox for newly uploaded permit decisions Standardized Excel import with validation and clear error messages Central conditions table with filtering, searching, sorting, and editing Assignment of authorities and specialist planners Deadlines, internal status, and completion tracking Comments and file uploads for each condition User invitations and email notifications Prepared authority emails PDF and ZIP project exports Project archiving SaaS administration area Basic billing and invoice-draft functionality Staging and production environments Deployment, backups, monitoring, and technical documentation A detailed functional specification and initial UI concepts will be provided to shortlisted candidates. Required experience We are looking for someone with strong experience in: Building custom B2B SaaS products Full-stack web development React or a comparable modern frontend framework Node.js or another suitable backend technology Relational database design Multi-tenant application architecture Role-based access control Secure file uploads and cloud storage Excel import and validation Email services and notifications PDF generation and data exports Cloud deployment, backups, security, and monitoring Designing maintainable APIs for future AI integrations Experience with document-management systems, workflow applications, construction software, or compliance platforms would be an advantage. How we would like to work We are looking for a developer who communicates clearly, raises technical concerns early, and actively proposes practical solutions. The project will be managed in defined milestones, starting with architecture and UX/UI validation before the main development begins. We expect: Regular written progress updates Clear milestone planning Early delivery of clickable screens or working modules Development in our Git repository Documented architecture and deployment process Clean, maintainable, and transferable source code Transparent communication regarding risks, assumptions, and additional costs English communication is fully acceptable. The Website finally needs to be in German. Please include in your proposal Please provide: Examples of comparable SaaS platforms you have built Your recommended technology stack Your proposed architecture Your estimated timeline Your estimated total cost or effort by project phase Your availability Whether you will personally complete the work or involve a team Your approach to testing, deployment, security, and ongoing maintenance Please also explain how you would structure the Excel import so that a future AI extraction service can use the same validation and import pipeline.