Telegram Mini App: Multi-Seller Marketplace

We are building a multi-seller marketplace as a Telegram Mini App. Full project details shared after NDA signing.

TECH STACK — OUR PREFERENCE (OPEN TO DISCUSSION):

Next.js 15 + TypeScript (Telegram WebApp SDK)
Node.js + Express or Python FastAPI
PostgreSQL + Redis
Docker + Vercel or Hetzner deployment
Custom payment API integration (local mobile payment + international payment)

We are open to discussing the architecture and tech stack during the design phase. If you have a better approach for our use case, we want to hear it.

ARCHITECTURE REQUIREMENT:
The backend must be API-first and fully decoupled from the Telegram layer. The same API must support web and mobile clients in the future with no backend rebuild. Service-oriented structure with clear service boundaries from day one.

WE WILL NOT CONSIDER:

WordPress or WooCommerce solutions
Bot-only experience
Monolithic architecture
Full upfront payment requests

Full specification documents shared after NDA signing.
TO APPLY — ANSWER ALL 6 QUESTIONS:

Share a live Telegram Mini App you have built — not a bot.
Have you built a multi-seller marketplace? Describe briefly.
How would you structure the backend to support Telegram today, web in 6 months, mobile in 12 months?
Your proposed timeline with milestone breakdown?
Do you work alone or with a team?