Senior Java Engineer, OKX Pay Smart Account Team.

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!