DZSA-02-Senior Software Engineer, AI Agent & Search - LegalOn

We are a global leading company providing Professional AI — products that combine deep domain expertise with advanced AI.
Since our founding in 2017, we have focused on developing AI-powered legal technology, raising a total of approximately JPY 28.6 billion to date. In 2022, we established our U.S. entity, and in 2025, we accelerated our global expansion further through our first M&A, welcoming Germany-based Fides Technology into our group.
Our flagship product, LegalOn, is currently available in Japan, the United States, and the United Kingdom. In September 2025, just six and a half years after launch, LegalOn surpassed JPY 10 billion in ARR. Beyond legal, we are expanding into other highly specialized domains with products such as WorkOn, DealOn, and GovernOn, leveraging AI to support complex professional work.
Through our strategic partnership with OpenAI, we incorporate cutting-edge technologies such as AI agents into our product development. By delivering solutions that address a wide range of business challenges, we empower our customers to achieve better outcomes.

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

Key Responsibilities

As LLMs and AI agents continue to reshape product experiences, search and recommendation are rapidly becoming core technologies that enable AI agents to perform complex professional tasks, rather than simply standalone features. In our global product “LegalOn,” the search and recommendation platform is also one of the most mission-critical systems.

In this role, you will join a team responsible for improving specific areas of the user experience in “LegalOn.” Leveraging your expertise in search and recommendation, you will play a core role in designing and developing AI agent features to deliver highly valuable product experiences for users. We welcome people who are genuinely interested in search and generative AI technologies and who enjoy shaping user experiences through collaboration.

Mission and Challenges

• Leverage expertise in search, recommendation, and AI to maximize user value as part of a team responsible for improving specific areas of the user experience
• Collaborate with product managers and related teams to explore various possibilities for what features to deliver to customers
• Drive concrete and actionable development plans to ensure the successful delivery of product features
• Contribute to broader product development beyond search and recommendation to enhance the overall user experience
• Mentor team members in designing sustainable and highly maintainable software systems

What You’ll Do

• Design, build, and deliver a wide range of search, recommendation, and Agent features/APIs
• Integrate LLM-powered applications with search and recommendation features to expand product capabilities
• Proactively maintain and operate search and recommendation systems to ensure high availability and performance
• Collaborate cross-functionally to investigate production issues in search, recommendation, and Agent systems, establish quantitative evaluation metrics, and drive continuous improvements
• Develop a deep understanding of user behavior regarding search and recommendation to contribute to broader product development and ensure a cohesive user experience

Development Environment / Tools

Backend: Go, Python

For additional details, please refer to this notion page:
https://legalforce-recruit.notion.site/LegalOn-Technologies-f5ebe38a6009428ab0fb1714efd3c90a

Required Skills / Qualifications

• 5+ years experience in software engineering
• Experience in one or more of the following
  • Experience developing AI agent features leveraging LLMs
  • Experience developing large-scale search or recommendation systems
  • Experience developing or improving machine learning models
• Experience designing and developing production-grade backend services using Python or Go
• Experience improving development processes by leveraging AI tools
• 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
• Business-level communication skills in Japanese (JLPT N1 or equivalent)

Preferred Skills / Qualifications

• 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 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
• 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