How I Built a Multi-Tenant B2B Wholesale Platform with Next.js 14 and Supabase

I spent the last few months building a complete B2B wholesale operating system from scratch. Here's a deep dive into the architecture and challenges I solved. The Problem Most small wholesale suppliers still manage orders over WhatsApp, email, and spreadsheets. There's no affordable tool built specifically for them. I set out to build one. Tech Stack Next.js 14 (App Router) Supabase (PostgreSQL + Row Level Security + Auth) Stripe Connect (buyers pay merchants directly) Tailwind CSS + Framer Motion Resend (transactional emails) Vercel (deployment) Architecture Decisions 1. Multi-Tenancy with Row Level Security Each merchant gets their own store. Instead of separate databases, I used Supabase RLS to isolate data at the row level: sql CREATE POLICY "Users can only see their own store's products" ON products FOR SELECT USING (store_id IN ( SELECT id FROM stores WHERE owner_id = auth.uid() ));