Senior Java Lead Engineer

Job Description Join a mission-critical platform team supporting order management systems used by millions of merchants. You will lead design, improvements, and operations while collaborating closely with internal stakeholders in Japan. Key Responsibilities: - Lead system design (basic to detailed) and development for web applications - Collaborate closely with internal teams to deliver high-quality solutions - Participate in a large-scale infrastructure migration project for existing systems - Improve and enhance existing applications, including feature additions - Handle system investigations, bug fixes, and production incident responses - Support full lifecycle delivery: design, development, testing, and release - Contribute to system quality improvements and user experience enhancements - Build scalable and maintainable web systems, including batch processing Profile & Requirements: - 5+ years of Java development for web applications and batch processing - Strong understanding of memory management (GC), thread safety, and exception handling best practices - Solid Oracle/SQL experience (3+ years), including complex queries, indexing, and execution plans - Ability to design with performance considerations in mind - Strong communication skills and ability to work collaboratively within a team - Hands-on experience across design, implementation, and unit testing Preferred qualifications: - Experience with Spring Framework - Experience in cloud environments (AWS, GCP, etc.) - Experience with Kubernetes or containerized development - API design experience (REST/SOAP) - SQL performance tuning experience - Technical leadership experience (design direction, code reviews, problem-solving leadership) Language Requirements: - Japanese: Business level (required for daily collaboration) - English: Not required