Marketplace APIs that connect buyers, sellers, and the payment and trust infrastructure between them.
We build API infrastructure for marketplace startups — Stripe Connect for split payments and seller onboarding, identity verification integrations, review system APIs, third-party service integrations, and the developer-facing API that lets your supply side build on your platform. Fixed scope, fixed price.
Your marketplace is manually reviewing seller applications, manually splitting payments, and manually handling disputes. Every manual process in a marketplace is a ceiling on how many transactions per day you can actually process.
Marketplace platforms have more integration surface area than almost any other product type. The buyer-side needs payment processing, identity verification (for high-trust categories), review collection, and dispute management. The seller-side needs onboarding, KYC verification, payout management, listing management APIs, and inventory or availability sync. The platform itself needs fraud detection, tax reporting (1099-K for US payees), and the trust infrastructure that makes transactions safe for both sides without human review of every transaction.
The payment architecture is the most critical and most complex. Split payment marketplaces — where the platform takes a commission and the seller receives the remainder — require Stripe Connect, not standard Stripe. Stripe Connect has two primary account types (Express and Custom) with different levels of seller control over their payout experience. Express is faster to implement but provides less flexibility for the seller onboarding UI. Custom provides full control but requires the marketplace to build and maintain the full onboarding flow. The choice between them depends on the seller experience you want to provide.
Identity verification is the second critical integration. Marketplaces in high-trust verticals (home services, childcare, professional services) need identity verification and credential checking before a seller can transact. Persona and Alloy have API-based identity verification flows with structured decision outputs that can integrate directly into the onboarding workflow without manual review of every seller.
A marketplace API layer with automated seller onboarding, Stripe Connect payment splitting, identity verification, automated dispute workflows, and a supply-side API that lets sellers integrate your platform into their operations.
Stripe Connect integration
Express or Custom Stripe Connect implementation for split payments. Seller onboarding flow (KYC data collection, bank account, identity verification via Stripe). Commission split calculation on charge completion. Seller payout scheduling (instant, daily, weekly). 1099-K tax form generation for qualified sellers.
Identity verification integration
Persona or Alloy API integration for seller identity verification — government ID capture, liveness check, database verification. Decision webhook processing to gate seller activation on verification result. Manual review queue for edge cases.
Seller/supply-side API
REST API for sellers with significant transaction volume who need to integrate your platform into their operations systems — inventory updates, listing management, availability calendars, order fulfillment webhooks. API key authentication with seller-scoped access.
Fraud detection integration
Stripe Radar custom rules for payment fraud. Sift or Kount integration for account takeover and listing fraud detection where transaction volume justifies the investment.
Dispute and refund automation
Structured dispute workflow with evidence collection templates per dispute reason. Automatic evidence submission to Stripe for eligible dispute types. Refund policy enforcement via API rather than manual case review. Built on Next.js API routes, Stripe Connect, Postgres, Persona/Alloy identity verification.
One honest number to start.
Fixed-scope, fixed-price. The number below is the starting point — final scope is built from your brief.
A marketplace API layer with automated seller onboarding, Stripe Connect payment splitting, identity verification, automated dispute workflows, and a supply-side API that lets sellers integrate your platform into their operations.
Three steps, every time.
The same repeatable engagement on every project. No surprises, no mystery, no billable ambiguity.
Brief & discovery.
We send you questions, then get on a call. Output: a written scope with every step, feature, and integration listed.
Build & ship.
Fixed schedule, weekly reviews. No scope creep unless you change the scope — and if you do, we reprice it transparently.
Warranty & retainer.
30-day warranty on every launch. Most clients stay on a monthly retainer for ongoing features and maintenance.
Why Fixed-Price Matters Here
Marketplace founders are optimising for transaction volume. Every manual process in the trust and payment layer is a ceiling on daily transaction capacity. Fixed-scope API work with a defined delivery date is how you plan the path to removing those ceilings.
Related engagements.
Questions, answered.
Express is right if you're willing to use Stripe's hosted seller onboarding and payout UI — it's faster to implement and Stripe handles the KYC compliance. Custom is right if you need full control over the seller onboarding UI and want the payout experience to be native to your product. Custom requires more implementation time but provides better seller UX for markets where the seller brand experience matters.
Stripe Connect supports payouts to sellers in 35+ countries with country-appropriate bank account formats. International payouts require collecting country-specific KYC data during onboarding. Tax reporting requirements vary by country. We configure the multi-country payout support for the specific countries your seller base operates in.
Seller-to-platform inventory push via API requires the seller's system to call your API when inventory changes. For sellers without a system capable of API calls, a webhook/polling hybrid or bulk update endpoint is more appropriate. We scope the supply-side API based on the technical capabilities of your seller population.
Stripe Connect integration, seller onboarding, identity verification, and supply-side API typically runs $35k–$75k. Custom Connect implementation and fraud detection integrations are the main variables. Fixed-price.
10 to 14 weeks for a production marketplace API layer with payments and identity verification operational.
Tell Ryel about your project.
Describe what you’re building and what outcome you need. You’ll have a written, fixed-price scope within the week.