Seeking Web App Developer with Node.js , React , Databases, and AWS exp ( Full stack developer )

About the project We’re building a web application in the fintech domain. It’s live with early users, and we’re looking for an experienced full-stack developer to join our current developer. Your first job is to help us fix a set of existing issues and review our codebase, with a focus on security, data accuracy and reliability. What you’ll do Fix existing bugs. We have a few long-standing issues that need a developer who likes digging into hard problems. Review the code. You’ll audit the front end, back end and database for quality, security, performance and maintainability, and recommend improvements. Build and refine features across the front end (React) and back end (Node.js). Design and optimise the Supabase / PostgreSQL database, including schemas for transactions, accounts, balances and ledgers. Write and review row-level security (RLS) policies, database functions, triggers and migrations. Build Supabase Edge Functions and use Supabase Auth, Storage and Realtime where they fit. Integrate payment and financial APIs (Stripe, PayPal, Plaid or similar), including webhooks, subscriptions, coupons and refunds, using idempotent requests and proper retry handling. Implement secure authentication and authorization (role-based access, MFA, session handling). Build dashboards and reporting for financial data (transaction history, statements, exports, charts). Follow security best practices (encryption, secure API design, audit logging) and keep PCI DSS and GDPR requirements in mind. Write clean, documented, testable code and work with Git-based workflows. Join a short weekly call to prioritise next week’s work. Required skills JavaScript (ES6+) and TypeScript HTML5 and CSS3 React (hooks, context, state management), plus Next.js or Vite Node.js with Express or Fastify Supabase (Auth, RLS, Edge Functions, Storage, Realtime, supabase-js client) PostgreSQL (schema design, SQL queries, indexing, transactions, migrations) REST API design and API integration Tailwind CSS Git and GitHub workflows Web security basics (OWASP Top 10, XSS, CSRF, SQL injection) Fintech experience (strongly preferred) Payments with Stripe, PayPal or similar Banking and open banking APIs (Plaid, TrueLayer or similar) Transactional integrity: ACID transactions, double-entry bookkeeping, reconciliation Decimal-safe money calculations and multi-currency handling Subscription and billing logic, invoicing KYC/AML and identity verification flows Audit trails, rate limiting and fraud prevention Nice to have React Query / TanStack Query, Zustand or Redux Zod or similar schema validation Testing with Jest, Vitest, React Testing Library or Playwright CI/CD (GitHub Actions) and Docker AWS or other cloud infrastructure React Native AI/LLM API integration Details Time commitment: about 10 hours per week to start, with room to grow Type: freelance or contract, remote Longer term: ongoing support and maintenance for the right person