Senior Backend Engineer

This role suits a Senior Full-Stack Engineer with 4–8 years of experience, especially in Node.js, TypeScript, PostgreSQL, and React Native. Ideal for someone skilled in backend workflows, event-driven architecture, and mobile-first development, particularly in payments or financial services. Candidates should be confident owning epics end-to-end, integrating third-party systems, and collaborating within agile, remote teams.

1. What are some key considerations when integrating FPX or DOBW into a mobile platform?
   Considerations include adhering to PayNet protocols, handling asynchronous payment statuses, secure data transmission, and providing real-time user feedback via the mobile UI.

2. Describe how you would structure a NestJS service to handle payment initiation and callback handling.
   Separate controllers for initiation and callback endpoints, use services for business logic, and integrate middleware for logging and error handling; async flows can be managed using event emitters or Kafka.

3. What patterns would you use in PostgreSQL schema design for transactional systems?
   Normalize tables to avoid data redundancy, use indexed foreign keys for relations, apply proper transaction isolation levels, and design for auditability with status tracking and timestamps.

4. Explain how Kafka can be used in an event-driven payment architecture.
   Kafka allows decoupling services by publishing payment events (e.g., initiated, succeeded, failed), enabling other components to consume these events for reconciliation, notifications, or audits.

5. What are some challenges you might face using React Native for payment flows, and how would you address them?
   Ensuring secure credential handling, managing native modules for bank redirection flows, and gracefully handling slow or failed transactions via proper UI states and retry mechanisms.

6. How do you ensure type safety and maintainability in a large TypeScript codebase?
   Use strict compiler settings, shared interfaces for data contracts, modular architecture, and enforce coding standards through linting and code reviews.

7. How would you orchestrate a multi-step payment workflow using Temporal?
   Define workflows to manage payment steps (e.g., validate, initiate, confirm), use activities for isolated business logic, and apply retry and timeout policies for resilience.

8. Describe an experience where you integrated with a third-party payment system. What were the biggest challenges?
   Handling inconsistent API documentation, managing retries for unreliable endpoints, and synchronizing real-time and batch settlement data were primary issues, solved by thorough testing and async event processing.

9. What best practices do you follow when designing APIs for financial transactions?
   Use idempotency keys, detailed status codes, proper authentication/authorization, audit logging, and ensure data validation at both request and persistence layers.

10. What is your approach to debugging a failed payment reported by a user?
    Start with logs and trace IDs to reproduce the flow, check Kafka or Temporal events, validate third-party response data, and ensure the mobile app state matches backend transaction history.

Join a leading Singapore-based wealth management platform as a Senior Software Engineer and help expand payment capabilities into Malaysia through FPX/DOBW integration. You'll work in a cross-functional remote squad, tackling complex backend systems, mobile development with React Native, and system integrations using Node.js, TypeScript, PostgreSQL, and NestJS. This 6-month, full-time remote contract starts July 1, 2025, with core hours from 2–6 PM GMT+8. You'll collaborate with PayNet, banking partners, and internal teams on mission-critical fintech infrastructure. Ideal for engineers eager to grow in a high-impact, agile environment with cutting-edge technologies and regional exposure.