Web-Based Tariff/Import Duty Simulator

I’m looking for a strong full-stack developer to build a web-based tariff/import duty simulator similar in feel and functionality to Flexport’s tariff calculator https://tariffs.flexport.com/. The tool should allow users to input shipment details (country, transport mode, declared value, etc.) and receive a clear breakdown of estimated duties/tariffs/fees in a clean, interactive UI.

Key Features (MVP)

Interactive Calculator UI
Clean, modern interface (desktop + mobile responsive)
Form inputs: origin country, destination country, entry date, shipment value, transport mode, and other relevant fields
Real-time updates of results as inputs change
Results displayed in a clear breakdown (line items + totals)

Backend Calculation Engine

API endpoint(s) to process inputs and return results
Business logic designed so tariff rules can be updated over time
Validation for inputs and safe handling of missing/invalid values
Data Source Integration (Discuss Options)
Prefer integration with a reliable tariff/duty data source or API
If real data is not available within budget, propose a realistic approach (limited dataset, manual upload, admin panel, etc.)
Caching to reduce repeated calls and improve performance

Deployment

Deploy to Vercel/Render/AWS (open to recommendations)
Provide clear documentation for setup and future maintenance
Tech Preferences (open to alternatives if justified)
Frontend: React or Next.js

Backend: Node.js (Express/Nest) or Python (FastAPI)

Database: Postgres preferred
Optional: Docker

Deliverables
Working web app (MVP)
Source code in a Git repo
Documentation: setup, deployment, and how to update tariff logic/data
Basic tests (at least core calculation paths)

Milestones

UI prototype + flow (Figma or in-code)
Core calculator UI + basic backend endpoints
Data integration + calculation logic
Final polish + deployment + documentation