TECH-AI-102/EN- Senior Software Engineer - Search, AI

LegalOn Technologies is a global leader in legal AI solutions, trusted by more than 8,000 companies and law firms worldwide. The company empowers legal teams to review and negotiate contracts faster, with greater accuracy and confidence. Operating across Japan, the United States, and Europe, LegalOn is the first AI company from Japan to surpass ¥10 billion in annual recurring revenue (ARR) and has raised over $200M from leading investors including SoftBank and Goldman Sachs. It also has one of the largest and most global AI teams of any startups in Japan. In 2025, LegalOn achieved its first M&A by welcoming Germany's Fides Technology into the group, further accelerating global expansion. LegalOn combines LLMs, intelligent Agents and intelligent AI-driven workflows. Beyond legal, the company now offers specialized AI solutions including "CorporateOn," "CXOn," and "DealOn" to support diverse business domains requiring high expertise. In partnership with OpenAI, the company is redefining the legal AI landscape and developing innovative solutions for the future of professional work.

For more details about our company, products, and development organization:
https://legalforce-recruit.notion.site/LegalOn-Technologies-Candidate-Handbook-17d82a58637480d2836ae138e5b5ee95

Key Responsibilities

The search and recommendation systems at LegalOn Technologies power a wide range of features across multiple rapid-growth services. LegalOn Technologies is a leading global AI company, and Search and Recommendation is one of the most essential and mission-critical systems for our services. We are looking for a skilled Senior Software Engineer passionate about technology to design and implement various search/recommendation features and solve complex challenges to provide the best search experience to our customers. In this role, you will not only build core search/recommendation capabilities, but also develop a deep understanding of how users leverage these features within the broader product context, and contribute to surrounding product areas as needed.

What Mission and Challenges You’ll Take On

• Collaborate with product managers to explore what exciting features we would deliver to our customers, understanding how search and recommendation capabilities fit into the broader product experience, make a practical plan about how the work should be done, and take responsibility for the delivery.
• Contribute to product development beyond search and recommendation when needed, applying your engineering expertise to improve the overall user experience.
• Mentor team members to help design software systems in sustainable/maintainable ways.

What You’ll Do

• Design, build, and deliver a wide range of search, recommendation, and Agent features/APIs.
• Enhance functionalities such as integrating LLM-powered applications with search/recommendation features.
• Proactively maintain and operate search and recommendation features/APIs.
• Collaborate with team members and other teams to investigate performance and accuracy issues in search, recommendation, and Agent systems in production environments, establish quantitative evaluation metrics, and drive improvements.
• Develop a deep understanding of how users interact with search and recommendation features within the product, and contribute to adjacent product areas to ensure a cohesive user experience.

• BS degree in Computer Science, Mathematics, or other technology-related majors.
• 5+ years experience in search and software engineering.
• Basic knowledge of data structures and algorithms.
• Hands-on expertise in building highly reliable and performant web backend systems.
• Hands-on experience with one of the Cloud Infrastructure Services: AWS, GCP, or Azure
• Ability to communicate in Japanese on a daily basis (JLPT N2 or compatible experience)

• MS or Ph.D. degrees in Computer Science, Mathematics, or other technology-related majors.
• Hands-on experience in Apache Lucene, Elasticsearch, or Solr.
• Hands-on experience in developing Agent applications and related component technologies such as LangChain, Ragas, LlamaIndex, etc.
• Hands-on experience in Python or Java.
• Hands-on experience in machine learning and natural language processing.
• Experience mentoring/training junior engineers.
• Leadership experience in large-scale projects or teams (10+ members) with a proven track record of delivering results
• A proactive attitude towards learning and adopting new technologies, including AI-powered efficient development and task execution
• Strong communication skills, with the ability to work effectively across diverse cultures in both English and Japanese
• Experience contributing to product features across multiple domains or technology areas, beyond a single specialization

• Proactively identify team and product challenges, take autonomous action toward solutions, and see them through to completion with full accountability
• Share expertise generously to help maximize the overall output of the team
• Collaborate effectively within and beyond the team, leading constructive discussions and sound decisions
• Think beyond your area of specialization — stay curious about how users experience the product as a whole and proactively broaden your domain knowledge