Senior Software Engineer - Cloud Platform for SMEs (Full-Stack)

Overview
A rapidly growing fintech SaaS company is seeking a Senior Software Engineer to join its Partner Product Development team in Tokyo. The team focuses on building advanced cloud solutions that empower professional service firms (such as accounting and consulting professionals) to better support small and medium-sized businesses (SMBs).

This role offers the opportunity to develop high-impact products used by a large market share of professional firms and contribute to digital transformation initiatives across Japan.

Responsibilities

• Design, develop, and operate scalable web applications in a full-stack environment
• Contribute to product development across frontend and backend (no strict separation)
• Collaborate with cross-functional teams using Agile/Scrum methodology
• Work closely with product managers to validate requirements and improve user workflows
• Design cloud infrastructure and ensure performance, scalability, and reliability
• Leverage generative AI and development tools to enhance productivity and quality

Tech Stack

• Backend: Kotlin, Java, Ruby on Rails, GraphQL
• Frontend: React, Next.js, TypeScript
• Infrastructure: AWS, Docker, Kubernetes, Terraform
• Data & Middleware: MySQL, Kafka
• CI/CD: GitHub Actions, CircleCI, Argo CD

Requirements

• 5+ years of experience in web application development
• Strong experience in at least one of the following:
  • React / Next.js / GraphQL
  • Java / Kotlin / Spring Boot
  • Ruby on Rails
• Experience in building and deploying cloud-based systems
• Interest in working as a full-stack engineer
• Strong product mindset and ability to understand user workflows
• Ability to communicate in English in a professional environment

Preferred Qualifications

• Conversational Japanese
• Experience with microservices or system architecture design
• Experience in DevOps and container environments
• Familiarity with AI tools or AI-assisted development
• Experience in Agile/Scrum teams

Work Environment & Benefits

• Hybrid work (minimum 2 days in office per week)
• Flexible working hours system
• Latest hardware (Mac/Windows) and customizable setup
• Learning support including books and conference participation
• Internal mobility and career growth opportunities
• Health, insurance, and retirement benefits

Why Apply?

• Work on market-leading SaaS products supporting SMEs
• Join a forward-thinking engineering culture transitioning to English-first communication
• Be part of an AI-driven product evolution strategy
• High ownership and influence on product direction