Senior Fullstack Software Engineer

**About the company:** DMM Eikaiwa Minato-ku, Tokyo An online language platform that offers one-on-one lessons to students from around the world. We currently provide over 1 million lessons per month, making us one of the largest English schools on the internet. **Responsibilities:** Design, build, and maintain efficient, reusable, and reliable code across the entire stack. Collaborate with product and design teams to implement new features and user-facing applications. Adapt to and utilize proprietary, in-house data protocols and specialized internal design patterns. Identify bottlenecks and bugs, and devise solutions to mitigate these problems. Maintain strict standards for code quality, testing, and automation. Requirements Backend: Professional experience developing and maintaining web applications using Ruby on Rails. Frontend: Professional experience building responsive user interfaces using React. Solid understanding of object-oriented programming, relational databases, and state management. Experience integrating front-end components with back-end APIs. AI Tooling Demonstrated proficiency in integrating modern AI development tools (e.g., Claude, GitHub Copilot) into the daily workflow to maximize development velocity. A disciplined approach to AI utilization: leveraging tools for efficiency while maintaining full ownership of code quality, architectural integrity, and security. Nice to haves While not specifically required, tell us if you have any of the following. Hands-on experience training AI models (distinct from utilizing pre-trained model APIs or developer tool interfaces). Compensation ¥8,000,000 ~ ¥12,000,000 annually. **Requirements:** Backend: Professional experience developing and maintaining web applications using Ruby on Rails. Frontend: Professional experience building responsive user interfaces using React. Solid understanding of object-oriented programming, relational databases, and state management. Experience integrating front-end components with back-end APIs. AI Tooling Demonstrated proficiency in integrating modern AI development tools (e.g., Claude, GitHub Copilot) into the daily workflow to maximize development velocity. A disciplined approach to AI utilization: leveraging tools for efficiency while maintaining full ownership of code quality, architectural integrity, and security. **Nice to have:** While not specifically required, tell us if you have any of the following. Hands-on experience training AI models (distinct from utilizing pre-trained model APIs or developer tool interfaces). **Compensation:** ¥8,000,000 ~ ¥12,000,000 annually.