Stackr
B2C and B2B multi-vendor wholesale marketplace with automated vendor payouts
Technologies
Overview
Stackr is a multi-vendor wholesale marketplace built for three personas: customers buying at retail, store owners purchasing in bulk under MOQ rules, and wholesalers managing their catalog and receiving automated daily payouts. The platform covers the full commerce funnel: product discovery via Typesense full-text search, B2C and B2B cart flows with minimum order enforcement, atomic stock reservation at checkout, multi-vendor commission tracking, daily Stripe Connect payout batches, and EasyPost shipment tracking with webhook-driven status updates. Product embeddings via pgvector power similarity search, personalized recommendations, and frequently-bought-together calculations. The full stack runs in production: Hono API on Fly.io with a separate BullMQ worker process, Next.js frontend on Vercel, and Neon PostgreSQL with Drizzle ORM.
Key Highlights
- ✓Full multi-vendor marketplace live at stackr-nine.vercel.app with B2C, B2B, and wholesaler portals
- ✓Atomic stock reservation at checkout without database transactions (Neon HTTP driver constraint)
- ✓Daily Stripe Connect payout batch: aggregates commissions per wholesaler, executes transfers, sends email receipts
- ✓Typesense full-text and faceted search with real-time indexing via IPv6 Flycast networking on Fly.io
- ✓pgvector product embeddings (1536-dim, Voyage AI) for similarity search and personalized recommendations
- ✓EasyPost shipping integration with webhook-driven tracking status updates
- ✓Dual-channel cart (B2C and B2B) with MOQ enforcement and wholesale pricing tiers
- ✓Separate BullMQ worker process on Fly.io covering payout cron, search sync, email, and PDF
The Challenge
Problem Statement
Multi-vendor marketplaces carry compounding complexity: each order may span multiple wholesalers, each with their own pricing tiers, MOQ rules, commission rates, and payout schedules. Add to that a dual-channel cart (B2C vs B2B), atomic stock reservation without database transactions due to Neon's HTTP driver limitation, cross-domain auth cookies, and faceted search, all while keeping the frontend fast and the payout pipeline reliable.
This challenge required a solution that could scale to handle enterprise-level traffic while maintaining accuracy and providing a seamless user experience. The system needed to be production-ready from day one, with robust error handling and monitoring capabilities.
The Solution
Our Approach
Concerns are separated cleanly: a Hono API handles synchronous requests, a dedicated BullMQ worker handles async jobs (payouts, indexing, emails), and Typesense runs as a Fly.io sidecar for search. Atomic checkout uses SQL WHERE clauses (WHERE stock minus reserved_stock >= qty) instead of transactions. A daily cron at 02:00 UTC aggregates commissions per wholesaler and executes single Stripe Transfers for clean reconciliation. Cross-domain auth is fixed via a Next.js API rewrite that proxies all requests through the Vercel domain.
Architecture Overview
The Next.js frontend on Vercel serves all four user personas. All API calls are proxied through a Next.js rewrite to handle cross-domain auth cookies. The Hono API on Fly.io handles synchronous requests: catalog, search, cart, checkout, and dashboards. A separate BullMQ worker process consumes jobs from Upstash Redis for all async work: daily payout batches, Typesense re-indexing, email notifications, and shipment tracking polls via EasyPost.
Key Technical Decisions
Atomic checkout without DB transactions
Neon's HTTP driver doesn't support transactions. Stock reservation uses atomic SQL WHERE clauses to prevent overselling with no transaction boundary needed.
Alternatives Considered:
- •Drizzle transactions (incompatible with neon-http)
- •Optimistic locking with retries
Dedicated BullMQ worker process
Keeping async work (payout batches, Typesense sync, emails, shipment polling) in a separate Fly.io machine keeps the API low-latency and lets jobs survive API restarts independently.
Alternatives Considered:
- •In-process async handlers
- •Serverless cron functions
Daily batch Stripe Connect payouts
Batching all commissions per wholesaler into a single daily Stripe Transfer reduces API calls, simplifies reconciliation, and gives wholesalers a predictable payout cadence.
Alternatives Considered:
- •Real-time per-order transfers
- •Manual payout triggers
Next.js API rewrite for cross-domain auth
Frontend (Vercel) and API (Fly.io) are on different domains. Better Auth session cookies break cross-domain. A next.config.ts rewrite proxies /api/* through Vercel, keeping cookies on the same origin.
Alternatives Considered:
- •Custom domain with CNAME
- •JWT-only auth without cookies
Typesense over Elasticsearch for search
Typesense is lighter, faster to self-host on Fly.io, and has a simpler filter syntax. Real-time indexing with facets, sorting, and prefix search without Elasticsearch overhead.
Alternatives Considered:
- •Elasticsearch
- •Postgres full-text search
Technologies Used
Results & Achievements
User Roles
Admin, wholesaler, store owner, and customer, each with a dedicated dashboard
DB Tables
13 schema groups covering auth, catalog, commerce, AI, analytics, payments, and shipping
API Routes
Catalog, search, cart, checkout, wholesaler, admin, AI, and webhooks
AI Features
Product embeddings, similar products, recommendations, and frequently-bought-together
Integrations
Stripe Connect, EasyPost, Typesense, Cloudflare R2, Resend, and Upstash Redis
Key Achievements
- ✓
Full multi-vendor marketplace live at stackr-nine.vercel.app with B2C, B2B, and wholesaler portals
- ✓
Atomic stock reservation at checkout without database transactions (Neon HTTP driver constraint)
- ✓
Daily Stripe Connect payout batch: aggregates commissions per wholesaler, executes transfers, sends email receipts
- ✓
Typesense full-text and faceted search with real-time indexing via IPv6 Flycast networking on Fly.io
- ✓
pgvector product embeddings (1536-dim, Voyage AI) for similarity search and personalized recommendations
- ✓
EasyPost shipping integration with webhook-driven tracking status updates
- ✓
Dual-channel cart (B2C and B2B) with MOQ enforcement and wholesale pricing tiers
- ✓
Separate BullMQ worker process on Fly.io covering payout cron, search sync, email, and PDF
Want to Build Something Similar?
I specialize in building production-ready AI systems that scale. Let's discuss your project.
Related Content
Related Projects
BridgeAI
AI Integration Copilot that automates workflows across your business tools