Multivendor E-commerce Mobile/Web App Development

I want simple app store, here you can study my plan. And please bid only those who are interested to work under $100k.
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Infrastructure for my Multivendor E-Commerce Platform that supports:
• Brand New (vendors)
• Second Hand (users)
• Toggle-based marketplace
• Minimum cost,
• scalable later
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1. SYSTEM OVERVIEW

Mobile App / Web App
↓
Backend API Server
↓
PostgreSQL Database
↓
Image Storage (Bucket)
• Single backend (no microservices)
• Clean, low-cost, scalable base
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2. TECH STACK
Frontend
• Mobile App: Flutter or React Native
• Web: React
Backend
• Node.js (Express or NestJS)
Database
• PostgreSQL
Storage
• Cloud Storage (images)
Hosting
• Google Cloud Platform
CDN
• Cloudflare
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3. CORE LOGIC (IMPORTANT)
Marketplace Toggle (MAIN FEATURE)
At top of app:
[ Brand New ] [ Second Hand ]
Behavior:
• Brand New → show vendor products
• Second Hand → show user listings
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4. DATABASE STRUCTURE (SIMPLIFIED)
* Users Table
• id
• name
• phone
• password
• user_type → (user / vendor)
• created_at
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Products Table
• Id
• Title
• Price
• Category
• condition → (new / like_new / used)
• listing_type → (brand_new / second_hand)
• description
• location
• user_id
• created_at
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Product Images Table
• id
• product_id
• image_url
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Vendor Profile (optional simple)
• user_id
• shop_name
• shop PAN certificate image (KYC)
• shop_logo
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5. USER FLOW
Buyer
Open app
↓
Search / Browse
↓
Switch toggle
↓
View product
↓
Call seller
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Seller
Click “Sell”
↓
Upload images
↓
Add details
↓
Select:
• Brand New / Second Hand
↓
Post
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6. UI REQUIREMENTS (IMPORTANT)
Home Screen
• Logo
• Search bar (top)
• Toggle (Brand New / Second Hand)
• Product list
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Product Card
• Image
• Title
• Price
• Location
• Condition
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Post Product Screen
• Upload images
• Title
• Price
• Category
• Condition
• Location
• Toggle: Brand New / Second Hand
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7. DO NOT BUILD (NOW)
To keep cost low:
• Chat system
• Payment gateway
• Delivery system
• Complex filters
• AI features
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8. BASIC SECURITY
• HTTPS (SSL)
• Password hashing
• Admin panel (basic)
• Daily DB backup
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9. SCALABILITY (FUTURE READY)
This structure allows easy upgrade:
• Add chat
• Add payments
• Add vendor dashboard
• Add multiple servers
WITHOUT rebuilding system.
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FINAL SUMMARY (FOR DEVELOPER)
Build a simple marketplace app with:
• Single backend (Node.js)
• PostgreSQL database
• Image storage bucket
• Toggle system:
• Brand New
• Second Hand
• User types:
• Normal user
• Vendor
• Basic product posting + browsing
• Contact via phone
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