Multi-Vendor Marketplace

The Challenge

The client wanted to build a marketplace where independent sellers could list and sell products to a shared customer base — similar to a vertical-specific Amazon or Etsy. The complexity wasn't in the storefront; it was in the backend operations: each seller needs independent inventory, pricing, and shipping rules, while customers expect a unified checkout experience across multiple sellers. Commission calculation, seller payouts, and dispute resolution all needed to be automated.

Our Approach

The discovery phase focused on the two-sided nature of the marketplace: what sellers need (inventory management, order fulfillment, payout visibility) versus what buyers need (unified search, multi-seller cart, consolidated checkout). We also mapped the platform operator's needs: commission rules, seller verification, and marketplace health metrics.

Next.js powers the customer-facing storefront with server-rendered product pages for SEO. NestJS handles the backend with clear domain separation: catalog service, order service, payment service, and seller management service. PostgreSQL was chosen for the transactional data where multi-table consistency matters — a single checkout spanning three sellers must be atomic.

The commission engine supports configurable rules per seller and per category — percentage-based, flat-fee, or tiered based on volume. Payouts batch weekly with detailed breakdowns that sellers can audit.

Key Technical Decisions

Split-payment checkout. When a customer buys from multiple sellers in one cart, the payment is split at the gateway level — each seller's portion routes to their designated account minus commission. This eliminates the need for the marketplace to hold and redistribute funds.

Seller-level shipping rules. Each seller configures their own shipping zones, rates, and fulfillment timelines. The checkout aggregates these into a unified shipping estimate for the buyer while maintaining per-seller tracking after purchase.

Marketplace health dashboard. The platform operator sees real-time metrics: GMV, take rate, seller churn risk, product quality scores, and customer satisfaction by seller. This enables data-driven decisions about which sellers to promote or flag.

The Outcome

The marketplace launched with an initial cohort of 50 sellers and has grown to over 100 active vendors with 15,000+ products. The automated commission and payout system processes transactions without manual intervention. Seller onboarding — previously a manual process — now takes under 24 hours from application to active listing. We're currently building a recommendation engine and expanding the logistics integration to support same-day delivery in select regions.