Full-Stack Engineer | Generative AI / LLM | ¥9M–¥13M | Full Remote in Japan

📍 Position

Senior Full-Stack Engineer

💰 Salary

¥9,000,000 – ¥13,000,000 per year

Depending on experience and skills

🌏 Location

Full remote within Japan

You can work from anywhere in Japan.

The company also has an office in Tokyo, but there is no required number of office days.

⏰ Working Style

• Full flex-time system
• No core hours
• Flexible working hours: 6:00–22:00
• Standard working time: 8 hours per business day
• Average overtime: approximately 5–15 hours/month

💻 What You’ll Do

As a Full-Stack Engineer, you will go beyond simply implementing predefined requirements.

You will help answer an important question through engineering:

“How should humans and AI work together?”

You will be involved across the entire product development lifecycle, from product planning and architecture to implementation and continuous improvement.

Key responsibilities include:

• Design and develop new features utilizing LLM capabilities

• Work closely with Product Managers and UI Designers

• Develop both frontend and backend systems

• Improve RAG (Retrieval-Augmented Generation) systems together with ML Engineers

• Optimize streaming and asynchronous processing for LLM applications

• Improve response latency and overall user experience

• Design scalable architecture for 10x–100x future growth

• Improve CI/CD and engineering infrastructure

• Resolve technical debt and improve development productivity

• Participate in technology selection and architectural decisions

• Work directly with Sales, Customer Success, Product, Design, and ML teams

• Use real customer feedback to determine what should be built next

This is not simply a role for researching AI.

The goal is to turn AI into a practical product that people can use every day.

🛠 Tech Stack

Frontend

• TypeScript

• React / Next.js

Backend

• TypeScript

• Express

Database / Search

• Aurora MySQL

• Amazon OpenSearch Service

Infrastructure

• AWS

• Some Google Cloud / Azure

• Terraform

Development Tools

• GitHub

• Figma

• Notion

• Google Drive

Communication

• Slack

• Google Meet

The engineering team actively uses modern AI development tools such as:

• Claude Code

• Devin

• Gemini

• Cline

• Notion AI

🧠 Interesting Technical Challenges

Building production-grade LLM products requires solving problems that traditional software products do not always face.

For example:

• Designing UX around non-deterministic AI outputs

• Creating systems that guide users toward useful results without requiring AI expertise

• Balancing user freedom with system control

• Improving RAG accuracy

• Scaling AI applications for enterprise usage

• Maintaining enterprise-level security and reliability

• Rapidly integrating new ML research into production products

• Building an architecture that supports continuous experimentation without sacrificing stability

You will work closely with ML Engineers to prototype, test, and productionize new AI capabilities.

✅ Requirements

• Master’s degree in Computer Science or equivalent technical knowledge

• 5+ years of professional software engineering experience, or equivalent experience

• Strong experience with technologies similar to TypeScript and React / Next.js

• Experience developing applications on cloud platforms such as AWS or GCP

• Deep expertise in at least one technical area such as:

• Backend
• Frontend
• Infrastructure
• • Experience leading engineering teams or projects, or equivalent leadership experience
• • Native-level / highly advanced business Japanese communication skills

Candidates of any nationality are welcome, but very strong Japanese communication skills are essential.

A GitHub account or other technical portfolio will be required during the application process.

⭐ Nice to Have

• Experience building CI/CD pipelines or improving engineering processes

• Experience with automated testing

• Architecture design experience for large-scale or high-traffic systems

• Experience working with complex technical domains

• Experience developing Machine Learning or AI-related products

• Contributions to OSS or technical communities

🎯 What Kind of Engineer Are They Looking For?

Someone who:

• Takes ownership of technical and product challenges

• Is willing to work outside their existing area of expertise when necessary

• Can adapt to rapid changes in the business and organization

• Has strong professional ethics

• Learns from failure and turns it into future success

• Enjoys solving problems where there may not be a single correct answer

🎁 Benefits

• Full social insurance

• Stock option program

• AI development tools including Claude Code, Devin, Gemini and others

• Company-paid technical books

• Free drinks, coffee and snacks at the office

• Side jobs permitted with approval

• Onboarding and training programs

• Approximately 1.5 “No Meeting Days” per week

• Mentorship and tutoring programs

• Regular internal technical study sessions and paper-reading sessions

• Childcare support programs

• 120 annual holidays

• Weekends and national holidays off

• Paid leave provided from the start date

• Parental leave and maternity leave

📝 Selection Process

Document Screening

↓

Casual / HR Interview

↓

First Interview

↓

Final Interview

↓

Offer

Depending on the candidate, there may be approximately 1–3 interviews.

Interviews can be conducted online or in person.

A reference check is also part of the selection process.