Senior Java Engineer, OKX Pay Smart Account Team

Location: Singapore, Singapore Who We Are At OKX, we believe that the future will be reshaped by Crypto, ultimately contributing to every individual's freedom. OKX began as a crypto exchange giving millions of people At OKX, we believe that the future will be reshaped by crypto, and ultimately contribute to every individual's freedom. OKX is a leading crypto exchange, and the developer of OKX Wallet, giving millions access to crypto trading and decentralized crypto applications (dApps). OKX is also a trusted brand by hundreds of large institutions seeking access to crypto markets. We are safe and reliable, backed by our Proof of Reserves. Across our multiple offices globally, we are united by our core principles: We Before Me , Do the Right Thing , and Get Things Done . These shared values drive our culture, shape our processes, and foster a friendly, rewarding, and diverse environment for every OK-er. OKX is part of OKG, a group that brings the value of Blockchain to users around the world, through our leading products OKX, OKX Wallet, OKLink and more. Responsibilities Payment System Development: Design, develop, and optimize OKX Pay's payment backend systems; build highly available, high-concurrency, scalable payment infrastructure. Scan-to-Pay Capabilities: Contribute to core QR/scan-to-pay functionality across the critical path — payment code generation, scan recognition, order creation, payment confirmation, state transitions, timeout handling, risk-control validation, and exception compensation. Transaction Processing & Fund Flows: Design and implement secure, stable transaction processing systems covering orders, payments, clearing and settlement, reconciliation, refunds, and callback notifications. Crypto & Stablecoin Payments: Build crypto and stablecoin payment capabilities — on-chain transfers, transaction confirmation, address management, asset crediting, and payment-status synchronization — and integrate them with traditional payment experiences. System Stability & Problem Solving: Safeguard the stability of core payment flows; diagnose and resolve complex production issues including performance bottlenecks, data-consistency problems, fund-security risks, and abnormal transaction scenarios. Technical Optimization & Engineering Quality: Continuously improve system architecture, code quality, monitoring and alerting, exception compensation, and observability to raise the security, reliability, and maintainability of the payment system. Requirements Java Backend Experience: Solid Java development skills, fluent in Spring Boot and mainstream Java backend frameworks, with experience building high-concurrency, high-availability systems. Payments Domain Experience: Hands-on experience with payment systems and their core flows — payment orders, payment state machines, callback notifications, reconciliation, refunds, clearing/settlement, and exception compensation. Scan-to-Pay Experience: Background in scan-to-pay, acquiring, aggregated payments, merchant payments, wallet payments, or similar products, with familiarity across the full business and technical chain. System Design: Strong architecture design ability, capable of designing reliable transaction paths, state-transition mechanisms, and idempotency, retry, and compensation mechanisms. Data Consistency & Fund-Security Awareness: Understanding of the importance of data consistency, transaction handling, idempotency, deduplication, concurrency protection, risk-control validation, and fund security in payment systems. Crypto / Stablecoin Payment Understanding: Familiarity with the fundamentals of crypto and stablecoin payments and on-chain asset movement, including on-chain transfers, transaction confirmation, address systems, Gas, and crediting confirmation. Problem-Solving: Able to independently troubleshoot complex production issues, with strong log analysis, tracing, performance-optimization, and recovery skills. Ownership & Execution: Strong ownership; able to drive problems to resolution and ship projects in a fast-changing environment. Nice-to-Haves Stablecoin Payment Experience: Project experience with USDT, USDC, or other stablecoin payments, collection, settlement, crediting, or on-chain confirmation. Scan-to-Pay / Acquiring Experience: QR payments, merchant acquiring, aggregated payments, payment gateways, cross-border payments, or offline payment scenarios. Account & Ledger Systems: Experience with payment accounts, fund accounts, merchant accounts, ledger systems, clearing/settlement systems, or reconciliation systems. Blockchain Fundamentals: Familiarity with the transaction mechanisms, address models, and asset-transfer flows of EVM, Tron, Solana, or other mainstream chains. Risk & Compliance Awareness: Understanding of payment risk control, anti-fraud, limits, allow/deny lists, KYC/KYT, and AML mechanisms. High-Concurrency Transaction Systems: Experience building high-concurrency order systems, trading systems, payment gateways, acquiring systems, or finance-grade core systems. Who You Are A solid Java backend engineer with deep understanding of payment systems, especially scan-to-pay, acquiring, merchant payments, or wallet payments. You care not only about shipping features but also about fund security, system stability, exception compensation, reconciliation consistency, and the user's payment experience. You don't need to be a senior blockchain expert, but you have a basic grasp of crypto and stablecoin payments and are eager to explore new payment models that combine traditional payment experiences with on-chain assets. Perks & Benefits Competitive total compensation Comprehensive insurance coverage for employees and their dependants More that we love to tell you along the process! Notice: All official OKX vacancies are published on this website. While roles may appear on selected third-party platforms from time to time, information on other sites may be inaccurate or outdated. If in doubt, please apply directly through our official careers website. Information collected and processed as part of the recruitment process of any job application you choose to submit is subject to OKX 's Candidate Privacy Notice .