Senior Fintech Full-Stack Developer

We need an experienced fintech/full-stack developer or small team to extend an existing marketplace built with React, Node.js/NestJS, MongoDB, REST APIs, and cloud infrastructure. The work includes subscriptions, recurring billing, pay-per-view/download, featured content, multi-currency payments, provider abstraction, auditable ledger, referral rewards, agent revenue sharing, pending/available earnings, withdrawals, refunds, chargebacks, webhooks, reconciliation, admin controls, and KYC/KYB readiness. The system must separate platform/reward credits from withdrawable earnings and support future seller settlement and escrow. Please share relevant experience, recommended providers, fixed price, timeline, milestones, and team composition.