Product Engineer (Full-stack)

About this role

This role develops the early-stage products of Builder Work, a construction-industry-focused recruitment and job-change service. The central responsibility is to replace the current AI-and-spreadsheet matching process with an in-house multidimensional matching engine using ANDPAD field data. The engineer also develops AI functions, internal business systems, and new products such as web and app-based qualification support and reskilling services.

Responsibilities cover new product design and development from language, framework, and middleware selection through basic design, implementation, testing, and operations. The role includes building LLM-based automatic generation for work histories and job postings, career-rating functions, and operational platforms for career advisers and corporate sales teams. It also includes architecture design, middleware selection, analysis of behavioral logs, and service improvements based on quantitative and qualitative data.

Required qualifications include experience developing and operating web applications, experience developing a new service or business, the ability to turn prototypes into working products quickly, schema and query design for RDBMS or KVS systems, knowledge of web application security, and development and operations experience using frameworks. Candidates are also expected to align with the Builder Work and ANDPAD missions and to organize requirements and create products when specifications are not fully defined. No educational requirement is stated.

The posting welcomes development and operations experience with Ruby on Rails, Go, or Python; experience integrating generative AI or LLM APIs such as Claude or OpenAI into products; technical-lead experience; architecture and middleware selection; Docker or Kubernetes; scalability work; and knowledge of HR, recruitment, or the construction industry. The team uses AI coding agents such as Claude Code in implementation, code review, research, and testing, including standardized pull-request reviews, dependency checks, security checks, and end-to-end testing.

Employment is full-time with a three-month probationary period and no change to working conditions during probation. The work location is the Builder Work dedicated project office in Suidobashi, Tokyo. Work is generally office-based, with remote work available for consultation. Working hours are 10:00–19:00 under a flextime system with an 11:00–15:00 core time. Annual salary is 6–12 million JPY, determined according to experience and ability, and includes fixed overtime pay for 45 hours per month. Salary increases and bonuses are provided twice a year. Benefits include social insurance, book-purchase assistance, an employee stock ownership plan, commuting expenses up to 30,000 JPY per month, remote-work allowances, nearby-housing assistance, and other allowances. Holidays include two days off per week on Saturdays and Sundays plus public holidays, annual paid leave, special paid leave at joining, seasonal and year-end holidays, and childcare, nursing-care, and condolence leave.

The selection process generally includes two or three interviews, currently conducted online, plus a 30-minute human-resources meeting during one of the first two interviews. The process also requests reference letters from two people who have worked with the candidate through the back check system.