Senior AI SaaS Developer - AIMER Production Build

We are building AIMER, a multi-industry SaaS platform focused on AI Employees, customer communication, booking systems, business management, subscriptions, and third-party integrations. The UI/UX, technical blueprint, approximately 30 screens, backend logic, workflows, and product structure are already prepared. We are looking for a senior full-stack developer to turn the existing specification into a secure, scalable, production-ready SaaS. Core requirements include: - AI Employees and AI-powered workflows using OpenAI/LLMs - Multi-channel customer communication - Booking and calendar systems - WhatsApp Business integration - Shopify integration - Google and Microsoft calendar integrations - Stripe subscriptions and billing - Multi-tenant architecture with proper data isolation - Authentication, roles and permissions - Admin dashboard and business management - APIs and third-party integrations - Notifications and automated workflows - Secure database architecture and audit logging - Production deployment, testing and error handling The developer should be comfortable with modern full-stack technologies such as Next.js, React, Node.js/NestJS, PostgreSQL/Supabase, APIs, AI integrations, Stripe and cloud deployment. Security, privacy, scalability and reliability are important. The system should be built properly for real customers, not as a demo or temporary MVP. I already have the detailed specifications and visual references and will provide them to the selected developer. I prefer a milestone-based fixed-price contract. Please review the requirements carefully and provide: 1. Your proposed architecture and technology choices. 2. Estimated timeline. 3. Fixed-price estimate and milestone breakdown. 4. Relevant examples of similar AI SaaS projects you have built. 5. Any technical risks or questions you identify before development starts. We are looking for a long-term technical partner, not just someone to write code.