Senior Platform Engineer

This full-time senior engineering role works on shared application foundations for an integrated cloud software platform serving individual businesses and small and midsize companies. The potential areas include authentication, authorization and permissions, billing, application and approval processes, notifications, workflow execution, files, data aggregation, Pub/Sub, search, audit logs, public APIs, and AI agents.

The engineer will help define medium- and long-term technical direction and lead development that includes system design. The role requires ownership of delivery and impact, an overall optimization perspective, and work to evolve mission-critical foundations into systems that are more scalable and extensible as the business grows. Responsibilities also include strategically addressing technical debt and creating foundations that make development easier for engineers across the company. Assignment is determined based on prior experience and career interests, and duties may change depending on business conditions and suitability.

Required qualifications are approximately five or more years of backend development experience, experience using AI tools such as Claude beyond individual use and extending that use across a team, and experience participating in system development from requirements definition. Preferred experience includes developing billing or payment services; domain development related to access control; designing and developing internal or external APIs; designing, developing, and operating microservices; developing and operating services with at least 10 million monthly requests; migrating large legacy systems; leading large-scale refactoring; analyzing and improving system performance; designing and implementing distributed systems; decomposing monoliths into microservices; designing, developing, and operating internal libraries or shared foundations; and designing, developing, and operating AI agents.

The posting describes a preference for people who work backward from essential user value, can define an ideal future state, adapt by unlearning prior practices, and find practical breakthroughs through hands-on output in rapidly changing or complex situations.

The employment form is regular employment with a three-month probationary period. The work location is the Tokyo office at Art Village Osaki Central Tower 21F, 1-2-2 Osaki, Shinagawa-ku, Tokyo; the location may change because of business circumstances or an office move. Working hours use a specialized discretionary work system with eight deemed hours per day. Holidays and leave include Saturdays, Sundays, public holidays, year-end and New Year holidays, condolence leave, paid leave granted on the joining date, and six paid sick-leave days per year. Insurance includes employment, workers’ compensation, employees’ pension, and health insurance. Indoor smoking is prohibited. Online interviews are accepted.