Stellenbeschreibung:

Development of a Secure Customer Platform (Login + Klarna Subscription + Personalized GPTs per Customer)

I am looking for an experienced Full-Stack Developer (or a small team) to build a secure, stable, and GDPR-compliant SaaS platform.


The goal is to give each customer access—through a personal login—to their own AI-powered content generator (based on OpenAI’s Assistants API). Every customer will receive a dedicated GPT assistant, with its own system prompt, files, and context.

The customer portal must be personalizable per client (e.g. their logo, colors, and branding). Access will be managed through a monthly Klarna subscription.

Reliability and fault tolerance are critical. The system must be stable, error-free, and easy to maintain. In addition to the implementation, I also need an offer for ongoing support & system maintenance.


Core Requirements (MVP / Phase 1)
1. User Management & Authentication
   • User registration and login (email/password, social login optional)
   • Role-based access control (Admin, Subscriber, Free User)
   • Strict tenant separation (multi-tenant architecture)


2. Payments & Subscription Handling
   • Integration of Klarna subscriptions (preferably via Mollie or Adyen for stability)
   • Monthly recurring payments
   • Webhook/Callback integration: automatically activate or deactivate accounts depending on subscription status
   • Customer portal: update payment method, cancel subscription


3. Dedicated GPT per Customer
   • Each customer gets their own GPT assistant (custom system prompt + uploaded files/knowledge)
   • Chat interface (similar to ChatGPT UI) with saved conversation history
   • White-label customization: customer’s logo, colors, branding in their interface
   • Usage tracking (messages/tokens) per customer


4. Backend & Database
   • Store user data, subscription status, GPT usage, and assistant configurations
   • EU hosting only (e.g. Hetzner, OVH, Supabase EU)


5. Admin Dashboard
   • Manage customers, subscriptions, and GPT assistants
   • Assign/update customer branding (logo/colors)
   • Monitor system health, usage, and webhook logs


Non-Functional Requirements
• Stability: reliable, error-free with idempotent webhooks & retry logic
• Security: GDPR-compliant, EU data residency
• Scalability: able to support many customers with separate GPTs
• Monitoring: error tracking, health checks, usage metrics
• Documentation: clean handover documentation for operation & support


Tech Stack (suggested)
• Frontend: Next.js (React)
• Auth: NextAuth or Auth0 (EU tenant preferred)
• Backend: Node.js / Next.js API routes
• Database: Postgres (Supabase/Neon EU)
• Payments: Klarna integration via Mollie or Adyen
• AI: OpenAI Assistants API (dedicated assistant per customer, extendable to Mistral/Aleph Alpha)


Deliverables
• Fully functioning multi-tenant SaaS platform with Klarna subscription + GPT assistants per customer
• Customization option for logo/branding per client
• Source code in Git with documentation
• Test suite (unit + E2E)
• Admin dashboard for managing customers & assistants
• Deployment and operational documentation


What I Need in Your Proposal
• Implementation offer: timeline + fixed price for the complete MVP package
• Maintenance offer: monthly/annual cost for ongoing updates, monitoring & support
• References to similar SaaS projects (subscription-based or white-label systems)
⚠️ Important: Please only apply if you can provide a clear total price for the complete package (implementation + maintenance). Hourly offers will not be considered.


Collaboration
• Start: ASAP
• MVP timeframe: ~4–6 weeks
• Agile workflow with weekly updates
• Long-term partnership for maintenance & further development desired

NOTE / HINWEIS:

EN: Please refer to Fuchsjobs for the source of your application

DE: Bitte erwähne Fuchsjobs, als Quelle Deiner Bewerbung