AI Product Engineer, Sales LLM Product

Develop an LLM/AI product for the sales domain in a small development team working toward product-market fit. Collaborate with product managers, designers, engineers, business members, and customers from discovery through delivery. Investigate customer problems and sales processes, organize requirements, evaluate specifications, and test hypotheses about product experiences that improve sales results.

Design and implement core LLM features using multimodal opportunity and sales-activity data, including prompt and context engineering. Build continuously with Kotlin, Python, Next.js, and TypeScript; use feedback and usage data to implement improvements and refine customer and business value. Design architecture for scale and maintainability, address technical debt, performance, security, and reliability, and improve quality through code and design reviews.

Improve productivity through automation, development-flow changes, and knowledge sharing. Cursor, Claude Code, and Gemini are used for AI-driven development. Design and implement integrations with external SaaS products and APIs, including Salesforce, using customer environments and operational data to improve those integrations.

Required experience includes at least five years designing and implementing web applications; active involvement in technical decisions, design policies, and implementation leadership; technical leadership in a small team; code and design reviews; process improvement, productivity improvement, automation, or enablement; collaboration with product managers and business members on requirements organization, specification review, and requirements definition; and advancing a product through rapid hypothesis testing where there is no predetermined correct answer.

Preferred experience includes developing or prototyping products incorporating LLMs or generative AI; knowledge or experience with RAG architectures, vector databases, fine-tuning, prompt engineering, or context engineering; taking a new business or product from launch through growth; continuous improvement around PMF using customer feedback; TDD, DDD, or clean architecture; external SaaS/API integrations; AI-driven development with Cursor, Claude Code, or Gemini; and projects with overseas offices or external partners. The role values customer and business outcomes, understanding customer problems, workflows, and business strategy, and cross-functional work with product managers, designers, and business members. Longer-term contributions may include recruiting, technical communication, customer interviews, and building the development organization.

The stated environment includes Kotlin and Python on the server side; React, Next.js, and TypeScript on the frontend; AWS, Terraform, Fargate, and ECR for infrastructure; Aurora PostgreSQL for the database; Datadog synthetics and Playwright for testing; and Slack, Gather, Figma, Findy team＋, Notion, diaglams.net, Cursor, Claude Code, and Gemini for communication and other work.

This is a permanent full-time position. The probationary period is three months and may be extended to six months. Annual compensation is JPY 7,000,000–20,000,000, determined based on experience and skills, with salary increases twice a year in April and October under company rules. The workplace is the company's office at 3-11-24 Mita, Minato-ku, Tokyo 108-0073, and working from home is permitted. Working hours are 10:00–19:00 with a one-hour break, under a flextime system with core hours from 10:00 to 15:00. Holidays are Saturdays, Sundays, public holidays, and December 28 through January 3, with annual paid leave, bereavement leave, childcare nursing leave, caregiving leave, and menstrual leave. Benefits include company-leased housing, subsidies for PC-related equipment, and a corporate defined-contribution pension plan. Insurance includes health, employees' pension, employment, and workers' compensation. The scope of duties and workplace may be changed to locations designated by the company, including a place used for working from home.