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

SingaPay; Tangerang; On-site; IDR 320,000,000 - 520,000,000; Full time

Job summary

SingaPay is seeking an accomplished engineer to design and maintain scalable payment and e-wallet services. You will own Money-In and Money-Out processing, build backend APIs, and ensure transaction integrity and security in high-volume environments.

Ideal candidates have deep experience with PHP/Laravel or Golang, fintech platforms, and modern data stores. You will collaborate across product, QA, design, and ops to deliver reliable financial products.

Qualifications

• Experience building e-wallet or fintech platforms.
• Strong knowledge of payment systems and secure coding.
• Experience with relational and NoSQL databases.
• Familiar with message brokers like Kafka or RabbitMQ.
• Proven API design and integration experience.

Responsibilities

• Design, develop, and maintain scalable payment and e-wallet services.
• Build backend services and APIs for wallet transactions and balances.
• Implement ledger management, idempotency, and reconciliation.
• Develop Money-In and Money-Out processing with multiple channels.
• Ensure system reliability, performance, and secure integrations.

Skills

PHP/Laravel

Golang

Money-in/out

RESTful APIs

Security best practices

Idempotency

API design

Tools

MySQL

PostgreSQL

MongoDB

Redis

Kafka

RabbitMQ

Job description

• 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.
• 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.