Lead Full-Stack Developer – Autonomous AI & Live Commerce Ecosystem (Serbia)

Job Title: Lead Full-Stack Developer – Autonomous AI & Live Commerce Ecosystem (Serbian Market)
Project Overview
We are seeking an expert Full-Stack Developer or a small specialized team to build a next-generation marketplace platform tailored for the Serbian market. The project is fully architected with a detailed technical brief ready for implementation. The core value proposition is a "Zero-Input" user experience driven by autonomous AI agents and integrated Live Commerce.
Technical Stack
• Frontend: FlutterFlow (Native Flutter/Dart export capability required). 
• Backend: Firebase Blaze Plan (Firestore, Auth, Cloud Functions). 
• AI Engine: OpenAI GPT-4o-mini (Vision & NLP) + Pinecone (Semantic/Vector Search). 
• Video: Agora.io (Ultra-low latency broadcast streaming). 
• Automation: Firebase Cloud Functions orchestrated via Node.js. 
Key Modules for Implementation
1. Autonomous AI Agent System:
• Development of three specialized agents (Marketing, Sales, and Logistics) that utilize Firestore state documents to act autonomously. 
• Agents must handle automated listing optimization, real-time sales negotiations (within set discount bounds), and logistics mapping. 
2. Dynamic Enterprise Admin Dashboard:
• A comprehensive interface allowing the owner to modify B2B subscription tiers (e.g., €100/mo), B2C token pricing, commission rates, and logistics fees in real-time without code changes. 
3. Serbian Fintech & Compliance Integration:
• Implementation of NBS IPS QR codes via official REST API. 
• Card processing integration via CorvusPay. 
• Automated e-fiscalization through third-party ESIR providers (e.g., Teron or NetRačuni). 
4. Multi-Logistics Hub:
• Direct integration with PostExpress (Pošta Srbije) REST API for manifests, tracking, and shipping calculations. 
• Webhook support for secondary couriers (BEX). 
5. B2B SaaS Features:
• Bulk AI-powered inventory upload (handling 1,000+ items) via GPT-4o-mini Vision. 
• Advanced sales and conversion analytics for business accounts. 
Budget & Security Requirements
• Operational Safety: Implementation of a multi-tiered "Kill-switch" system with Firestore circuit breakers to prevent runaway API costs. 
• Future-Proofing: Architecture must be "Escrow-ready" to transition from direct payments to bank-intermediated escrow (e.g., OTP Banka) without core logic refactoring. 
• Confidentiality: A full Technical Brief (Firestore schemas, Cloud Function signatures, etc.) will be provided only after a signed NDA. 
Project Timeline & Budget
• Fixed Budget: €1,300.
• Timeline: 21 days (delivered in three 7-day sprints: Core, Fintech, Live). 
Interview Questions (Required for applicants):
1. How will you implement the NBS IPS QR generation to ensure it strictly follows the Serbian pipe-delimited text standard?. 
2. What is your strategy for optimizing OpenAI Vision API calls for a bulk upload of 1,000+ images while keeping costs under $1.00?. 
3. How will you handle the automated fiscal receipt generation immediately following a successful CorvusPay transaction confirmation?.