Lead Software Engineer – Full Stack / AI Product Development

Lead Software Engineer – Full Stack / AI Product Development

Location: Japan (Fully Remote Available)

Salary: JPY 9,000,000 – 13,000,000 per year

Employment Type: Full-time, Permanent

Work Style: Fully Remote / Flexible Working Hours

About the Opportunity

We are recruiting a Lead Software Engineer for a rapidly growing AI technology company in Japan specializing in Large Language Models (LLMs), generative AI, and enterprise AI solutions.

In this role, you will lead the development of next-generation AI-powered SaaS products, working across frontend, backend, and cloud infrastructure.

Beyond implementing features, you will help shape how humans interact with AI, solve complex engineering challenges, and drive technical decisions that support long-term product growth.

You will collaborate closely with product managers, UI/UX designers, machine learning engineers, and business teams to build scalable, reliable, and user-friendly AI applications.

Key Responsibilities

Full-Stack Product Development

• Lead the design, development, and implementation of AI-powered SaaS features.
• Develop frontend applications using TypeScript, React, and Next.js.
• Build and optimize backend APIs and services using TypeScript and Express.
• Collaborate with product managers and designers to deliver intuitive user experiences.
• Take ownership of technical decisions throughout the product development lifecycle.

LLM & AI Integration

• Integrate LLM technologies into enterprise applications.
• Collaborate with ML engineers to improve Retrieval-Augmented Generation (RAG) systems.
• Optimize streaming responses and asynchronous processing to improve user experience.
• Address technical challenges related to AI-generated content, performance, and reliability.

Architecture & Infrastructure

• Design scalable system architectures to support significant growth in users and usage.
• Improve application performance, reliability, and security.
• Reduce technical debt through refactoring and architectural improvements.
• Enhance CI/CD pipelines, development workflows, and cloud infrastructure.

Technical Leadership

• Lead technical discussions and architectural decisions.
• Mentor engineers and improve overall engineering practices.
• Collaborate with cross-functional teams to identify and prioritize product improvements.
• Establish development processes that balance innovation, speed, and quality.

Technical Environment

• Frontend: TypeScript, React, Next.js
• Backend: TypeScript, Express
• Database: Amazon Aurora (MySQL)
• Search: Amazon OpenSearch Service
• Cloud: AWS, Google Cloud, Azure
• Infrastructure: Terraform
• AI Development Tools: Claude Code, Devin
• Collaboration: GitHub, Notion, Figma, Slack, Google Meet

Required Qualifications

• Master's degree in Computer Science or equivalent knowledge and expertise.
• 5+ years of professional software engineering experience, or equivalent experience.
• Strong experience with TypeScript, React, Next.js, or similar technologies.
• Experience developing applications in cloud environments such as AWS or GCP.
• Deep technical expertise in at least one area: frontend, backend, or infrastructure engineering.
• Experience leading engineering teams or taking ownership of technical initiatives.
• Business-level to native-level Japanese proficiency, including the ability to evaluate Japanese-language AI outputs.

Preferred Qualifications

• Experience building and improving engineering processes, including CI/CD and automated testing.
• Experience designing scalable architectures for high-traffic or complex applications.
• Experience developing AI or machine learning-related products.
• Contributions to open-source software or technical communities.
• Experience working in fast-growing SaaS or technology companies.

Compensation & Benefits

• Annual salary: JPY 9,000,000 – 13,000,000, depending on experience and qualifications.
• Stock option program.
• Fully remote work from anywhere in Japan.
• Super-flexible working hours with no core hours.
• Flexible working hours between 6:00 AM and 10:00 PM.
• Side jobs and freelance work permitted with prior approval.
• Access to advanced AI development tools, including Claude Code, Devin, Gemini Pro, and Notion AI.
• Company-sponsored technical books and learning resources.
• 1.5 no-meeting days per week.
• Full social insurance coverage.
• Paid annual leave and parental leave.
• Weekends and Japanese national holidays off.
• Approximately 120 annual holidays.

Why Join?

• Build cutting-edge AI products: Work on real-world applications powered by Large Language Models and generative AI.
• Own technical decisions: Influence architecture, technology selection, and engineering strategy.
• Work across the entire stack: Contribute to frontend, backend, infrastructure, and AI integration.
• Solve meaningful engineering challenges: Address scalability, LLM response latency, RAG performance, and enterprise security.
• Enjoy a flexible work environment: Work remotely from anywhere in Japan with no core working hours.
• Grow as a technical leader: Help shape engineering practices and the technical direction of next-generation AI products.

Ideal Candidate

We are looking for an engineer who combines strong technical expertise with ownership, curiosity, and a collaborative mindset.

You should enjoy solving complex problems, exploring new technologies, and working beyond your primary area of specialization when necessary.

A passion for building practical AI applications that deliver real value to users is highly valued.

Application

If you are passionate about software engineering, AI product development, and technical leadership, we would love to hear from you.

Please apply with your updated resume and a GitHub profile or technical portfolio.

Recruitment Partner: United World Inc.