Senior Fintech / Full-Stack Developer — Marketplace Monetization, Payments & Payouts

Project Overview We have an existing multi-module marketplace built with React.js, Node.js/NestJS, MongoDB, REST APIs, cloud infrastructure, authentication/admin systems and GitHub. We need an experienced senior full-stack/backend fintech developer or small team for the next phase: SaaS/subscriptions, pay-as-you-go monetization, payments, referral rewards, agent revenue-sharing, financial ledger, withdrawals/payouts and financial administration. This is not a new marketplace build. The existing platform must be extended without breaking current functionality. Revenue Model & Objective The platform will monetize services/content through: SaaS / subscription plans Pay-as-you-go services Pay-per-view / paid information access Pay-per-download Paid/featured/promoted content Other configurable paid services Where revenue is attributable to an approved agent/referrer, a configurable share may become participant earnings. The system must maintain a clear relationship: Paid service/content → Customer → Payment → Platform revenue → Attribution → Agent/referral earning → Payout We need a secure, auditable financial layer supporting payments, subscriptions, entitlements, commissions/rewards, pending/available earnings, payouts, refunds/reversals, multiple currencies/providers and future KYC/KYB, BaaS and escrow. We do not want a simplistic single walletBalance. The system should use a proper ledger/transaction model separating platform credits/rewards from withdrawable earnings. Scope 1. Existing System Review Review the React/NestJS/MongoDB application, authentication, admin, infrastructure and relevant existing functionality. Extend the current architecture rather than unnecessarily rewriting it. 2. Monetization & Billing Build a configurable monetization engine supporting: Free/Premium plans Recurring subscriptions and configurable billing periods Pay-as-you-go / usage-based services Pay-per-view and pay-per-download Paid/featured content Country/currency-aware pricing Subscription activation, renewal, cancellation and expiry Failed recurring payments Entitlement/access control after payment Billing history Admin management of plans/pricing New paid services should be addable without hard-coding billing logic into individual marketplace modules. Typical flow: Service/plan → Price → Payment → Entitlement → Revenue → Attribution → Commission/reward → Ledger 3. Payment Infrastructure Implement provider-based payments covering: One-time and recurring payments Payment initiation/confirmation Server-side webhooks Success/failure/cancellation Refunds Idempotency/duplicate protection Provider references Currency-aware records Admin visibility We prefer a provider abstraction allowing different PSPs by country without rebuilding core financial logic. 4. Financial Ledger Implement an auditable ledger covering: Payment → Revenue → Referral/agent earning → Pending → Available → Withdrawal reservation → Payout → Refund/Reversal/Adjustment Every event must remain traceable to its originating transaction. Clearly separate: Purchased/platform credits Promotional/reward credits Pending earnings Available/withdrawable earnings Reserved payouts Paid earnings Purchased/promotional credits must not automatically become withdrawable cash. 5. Referral & Agent Earnings Implement configurable: Referral codes/links and attribution Qualifying actions/reward rules Fraud/self-referral controls Agent registration/admin approval Revenue attribution Commission/revenue-share rules Pending/available earnings Reversals/adjustments User dashboard and admin reporting Participant payouts represent approved earnings, not arbitrary peer-to-peer wallet transfers. 6. Withdrawals & Payouts Implement a controlled lifecycle: Available → Requested → Reserved/Review → Processing → Paid Include minimum withdrawal rules, balance validation, duplicate prevention, admin approval where required, verified payout destinations, provider references, failed/rejected payout handling and payout history. Architecture should support licensed payout providers rather than depend on manual transfers. 7. KYC/KYB Readiness Architecture should support verification states such as: Not Started / Pending / Verified / Rejected / Expired and allow payout eligibility to depend on verification. Established KYC providers are preferred over building identity/facial verification ourselves. 8. Refunds, Chargebacks & Reconciliation Refunds/disputes must correctly affect associated referral rewards and agent commissions. Use reversal/adjustment entries rather than deleting financial history. Provide reconciliation between the internal ledger and payment/payout provider records, with discrepancies visible to admins. 9. Security & Admin Include appropriate: RBAC/server-side validation Webhook signature verification Idempotency Audit logging Secure secrets handling Retry/error handling Transaction consistency Duplicate payment/payout protection Admin should have visibility into payments, subscriptions, refunds, rewards, commissions, earnings, withdrawals, payouts and reconciliation. Financial success must never depend only on frontend confirmation. Target Markets The platform is intended for multi-country operation, initially/planned around: Mozambique, Angola, South Africa, Namibia, Zimbabwe, Zambia, Malawi, Tanzania and DRC, with future international expansion. Architecture should support: Local currencies and USD where appropriate Country-specific PSPs/payment methods Cards/mobile money/local rails Local/cross-border payouts Country-specific KYC/KYB Multiple providers by jurisdiction Please recommend suitable payment, payout and KYC/KYB providers for these markets and identify important country/regulatory limitations. Future Readiness Not all are required now, but the architecture should allow: Additional countries/currencies → additional PSPs → KYC/KYB → automated payouts → licensed BaaS → seller settlement → buyer-to-seller payments → escrow/disputes. We want candidates who understand the difference between basic payment gateway integration and marketplace financial architecture. We do not intend to unnecessarily custody fiat or build regulated banking infrastructure where licensed providers are more appropriate. Required Experience Strong experience with React, Node.js/NestJS, MongoDB, REST APIs, cloud infrastructure, webhooks, payment APIs and RBAC. Preference for experience with: SaaS/subscription and usage billing Marketplace/multi-vendor payments Referral/commission engines Agent/seller payouts Financial ledgers/wallets Stripe Connect or equivalents Flutterwave/Paystack/dLocal or regional PSPs BaaS/embedded finance KYC/KYB Escrow/settlement Multi-currency systems Generic e-commerce checkout experience alone is not sufficient. Deliverables Technical/financial architecture Monetization/subscription engine Payment-provider abstraction/integration Financial ledger Referral/reward and agent commission systems Earnings/payout lifecycle Admin financial controls Refund/reversal handling Webhook processing and reconciliation Automated tests for critical financial flows Staging/production deployment Technical/API/handover documentation Budget & Timeline We intentionally have not provided a target budget or duration. Please independently propose: Total fixed-price estimate Recommended duration Milestones/payment structure Team composition Assumptions/exclusions Expected third-party/recurring costs Any functionality you recommend deferring, with reasons Your Proposal Must Answer Please avoid generic agency responses. Describe a relevant marketplace/SaaS payment, commission or payout system you have built. How would you implement subscriptions, pay-as-you-go and pay-per-use without hard-coding billing into individual modules? How would you separate platform credits/rewards from withdrawable earnings? How would you prevent duplicate webhook credits and handle commission reversals after refunds/chargebacks? PSP, marketplace-payments provider or BaaS—which would you recommend now and why? Which payment/payout/KYC providers would you recommend for our target African markets, and what limitations should we consider? How would you add currencies, countries and providers later? Which relevant payment/payout/KYC systems have you personally integrated? Who will work on the project? Provide your fixed-price estimate, duration and milestone breakdown. How would your architecture later support seller settlement and escrow? Please include relevant previous work.