Sr. Software Engineer (AI Product)

Applications: candidates may apply from outside Japan. Visa sponsorship: available. Japanese: Conversational. English: Business level. Japan Dev tags: Engineering, Web / Full-stack, Python, AWS.

About the AI Team

The AI team is responsible for developing and operating our proprietary AI models, including speech recognition and speaker diarization, as well as building LLM-powered features and designing and improving the optimal mix of multiple AI models.

By combining a range of AI technologies—including voice AI, LLMs, and our proprietary models—the team works to maximize product value while balancing real-time performance, accuracy, reliability, and cost.

About the Role

In this role, you will lead the design, development, and operation of product features powered by AI and LLMs.

We are not looking for someone who specializes primarily in AI model research and development. Instead, we are looking for an engineer with a strong software engineering foundation who can integrate technologies such as LLMs and voice AI into real-world products and turn them into meaningful value for users.

The systems you will work on combine multiple technologies, including LLMs, speech recognition, our proprietary AI models, and external APIs. You will continuously improve product value while balancing quality, latency, reliability, and cost.

You will take ownership of existing systems and be responsible for a broad range of areas, including feature development, architectural improvements, operational design, quality improvements, and technical decision-making.

Must haves

• Japanese language proficiency at JLPT N4 level or above
• 5+ years of professional software development experience
• Experience designing, developing, and operating web applications or backend systems
• Experience developing, maintaining, and improving production services
• Experience building production applications using Python
• Experience developing and operating systems in cloud environments such as AWS
• Strong interest in LLMs / generative AI, or hands-on experience integrating them into products
• Understanding of the characteristics and inherent uncertainty of AI / LLM outputs, with the ability to design and improve systems to ensure quality
• Ability to define, measure, and improve metrics tied to business value and user experience
• Ability to work autonomously while communicating effectively with relevant stakeholders