Senior Full-Stack Developer (Payment & E-Wallet Systems)

SingaPay• Tangerang, Banten, Indonesia (On-site)

We are looking for a Senior Full-Stack Developer (Payment & E-Wallet Systems) to join our IT team and play a key role in designing, developing, and maintaining high-quality web applications across both frontend and backend systems.

You will work closely with the engineering team to build scalable solutions, optimize existing applications, solve technical challenges, and ensure applications are properly deployed and functioning.

Senior Full-Stack Developer (Payment & E-Wallet Systems)

What We're Looking For

• Strong full-stack development experience with PHP/Laravel and/or Golang, preferably with Fiber or similar frameworks.

• Proven experience building and maintaining payment systems, digital wallets, or fintech applications, beyond basic third-party payment gateway integration.

• Strong understanding of e-wallet architecture and payment transaction lifecycles, including transaction processing, balance management, transaction history, and payment status handling.

• Hands-on experience developing Money-In and Money-Out systems, including:

  • Money-In: Virtual Accounts (VA), QRIS, Payment Links, bank transfers, payment gateways, and switching integrations.

  • Money-Out: Bank transfers, disbursements, PPOB, QRIS, payment gateways, and switching integrations.

• Solid understanding of financial transaction integrity, including double-entry ledger concepts, idempotency, duplicate transaction prevention, transaction consistency, and failure/reversal handling.

• Experience with payment reconciliation, settlement processes, refunds, and transaction monitoring.

• Strong understanding of RESTful APIs, authentication, authorization, OAuth2, JWT, and secure API integrations.

• Experience with relational and/or NoSQL databases, such as MySQL, PostgreSQL, and MongoDB, including query optimization and transaction management.

• Familiarity with Redis, Kafka, RabbitMQ, or other message-broker systems for asynchronous processing and event-driven architectures.

• Proficiency in frontend technologies, including HTML, CSS, JavaScript, and ReactJS, Svelte, or VanillaJS.

• Understanding of secure software development practices, particularly for applications handling financial transactions and sensitive data.

• Experience troubleshooting production issues, optimizing system performance, and maintaining high availability and reliability.

• Familiarity with AI-powered coding assistants such as Claude Code, DeepSeek, or Codex is a plus.

What You'll Do

• Design, develop, and maintain scalable full-stack applications for payment and e-wallet services.

• Build and improve payment processing capabilities across Money-In and Money-Out flows, including bank, QRIS, payment gateway, and switching integrations.

• Develop backend services and APIs that support wallet transactions, balance management, transaction histories, and payment status tracking.

• Implement reliable financial transaction processing, including ledger management, idempotency, transaction consistency, and error handling.

• Develop reconciliation, settlement, refund, and transaction monitoring capabilities.

• Build frontend interfaces and integrate them with secure backend services.

• Optimize database performance, caching, asynchronous processing, and message-queuing systems.

• Identify and resolve production issues related to payment failures, transaction discrepancies, performance bottlenecks, and system reliability.

• Collaborate with Product, QA, Design, and other engineering teams to deliver reliable financial products.

• Contribute to system architecture, code reviews, technical decisions, and engineering best practices.

Preferred Qualifications

• Previous experience building an e-wallet, digital payment platform, payment gateway, payment switching system, or other transaction-heavy fintech application.

• Experience handling real-world financial transactions in production environments.

• Understanding of payment security, audit trails, and controls for preventing inconsistent or duplicate financial transactions.

• Experience designing scalable and fault-tolerant systems for high-volume transaction processing.