Senior Backend Developer - Node,js (NestJS) Fintech Experience Mandatory

A Senior Backend Developer, you will be responsible for designing, developing, improving,
and maintaining WonnPay's backend platform. You will work closely with the CTO, engineering team, product team, QA, compliance, and external technology partners to build secure, scalable, and reliable backend services. The ideal candidate should be comfortable working independently, making technical decisions,
reviewing other engineers' work, and taking ownership of backend services from design
through production deployment and monitoring

Key Responsibilities:

Backend Architecture & Development
● Design, develop, and maintain scalable backend services using Node.js, NestJS, and TypeScript
● Design robust and maintainable backend architecture for fintech and transaction-based applications
● Develop secure and well-documented RESTful APIs
● Define service boundaries, API contracts, database structures, and integration patterns
● Identify and resolve architectural, performance, and scalability issues
● Refactor legacy or poorly designed backend components when required
● Ensure backend systems are designed for reliability, availability, and maintainability

Database & Data Management
● Design and optimize PostgreSQL databases and relational data models
● Design database schemas, indexes, relationships, migrations, and constraints
● Work with TypeORM or equivalent ORM technologies
● Optimize complex queries and database performance
● Ensure transactional integrity and data consistency
● Design appropriate approaches for handling concurrent transactions and race conditions
● Implement backup, recovery, and data-integrity best practices

Fintech & Transaction Systems
● Develop backend services supporting financial transactions, wallets, payments, and digital assets
● Ensure transaction processing is reliable, traceable, and idempotent
● Handle transaction states, retries, failures, reversals, and reconciliation
● Implement appropriate validation and business rules for financial operations
● Build systems that maintain accurate transaction and wallet balances
● Understand and apply principles of auditability, traceability, and financial data integrity

Third-Party Integrations
● Design and maintain integrations with external APIs and service providers
● Work with payment providers, KYC/AML providers, card issuers, blockchain providers,