【Senior Software Engineer】Japan & US - B2B2C Marketplace

Join a globally expanding e-commerce company dedicated to extending the lifespan of devices such as smartphones and tablets. The company has built an end-to-end ecosystem with multiple in-house products serving both B2C and B2B customers, and is now developing new SaaS solutions powered by generative AI.

As a startup fully backed by a major global enterprise, they combine the speed and innovation of a startup with the financial stability of a large corporation - achieving strong revenue growth despite its young age and successfully expanding into the US market.

Key Responsibilities

• Design, develop, and maintain backend systems and APIs (Go / Python)
• Integrate with internal and external APIs via HTTP and gRPC
• Design and manage databases on CloudSQL (PostgreSQL, MySQL)
• Ensure system reliability through release management, monitoring, and incident response
• Support team best practices, documentation, and code quality improvement
• Collaborate closely with product managers and business stakeholders to translate requirements into scalable solutions
• (For GenAI projects) Build and operate AI Agent and RAG platforms, develop connectors for data sources, and construct data vectorization systems

Why join

• Option to transfer internally to their New York office
• Very competitive compensation and ongoing expansion of their benefits and bonus system
• Flexible working hours and hybrid work system
• 20+ days PTO per year + childcare, family care leave etc.

• 5+ years of backend development experience for web applications
• Experience in service architecture, system design, and technology selection
• Hands-on experience with relational databases and cloud infrastructure (GCP, AWS)
• Solid understanding of containers, databases, and information security
• Business-level Japanese (JLPT N2 or above) and English
• Practical use of ChatGPT, Gemini, or similar AI tools to enhance productivity

Preferred Experience

• Development experience in Go and Python
• Building API systems using gRPC and Protocol Buffers
• Experience with warehouse management systems (WMS) or DWH integration
• Experience leading backend design or team projects
• Knowledge of multi-tenant SaaS architectures and authentication systems
• Familiarity with GenAI development (AI Agents, RAGs, vector databases, LangChain, Vertex AI)