【Senior Backend Engineer(Python)】AI SaaS / Hybrid / JLPT N3～

★Senior Back End Engineer (AI Agent Framework) | AI Consulting Services

• Japanese: Conversational Level Required

◆ Hybrid Work

◆ Start-up Company

◆ Great Welfare

◆ Annual Salary： 10 million ～ 18 million yen.

-------------【About the company】-------------

The company aims to dramatically enhance the potential of the workforce by leveraging AI technology. Established in April 2023, the company drives cutting-edge AI research and development both domestically and internationally.

A primary focus is the development of AI Agents, providing innovative products and solutions powered by Large Language Models (LLMs). Through these initiatives, the company achieves significant productivity gains and operational efficiency across various industries.

By capitalizing on its startup agility to ensure flexible and rapid decision-making, the company integrates the latest technological advancements ahead of the curve to deliver optimal solutions to its clients. Furthermore, a diverse team with an international perspective bolsters its competitiveness in the global market.

The company is dedicated to creating new value and contributing to the progress of society through the transformative power of AI. The company's goal is to lead AI innovation and co-create a future where technology empowers people to achieve more.

-------------【 Job Description】-------------

【Recruitment Background】

With rapid business expansion anticipated, the company is seeking a Senior Backend Engineer who can lead both R&D in advanced technical domains and the practical implementation of products.

Specifically, as the company pushes forward with research and large-scale development in the AI Agent field, there is an urgent need to strengthen the engineering team responsible for developing the core backend frameworks. The company is looking for a professional who can architect the foundational systems that will support the next generation of AI-driven social infrastructure.

【Role】

In this role, you will lead the functional enhancement and performance optimization of the AI Agent Framework, which is utilized cross-functionally throughout the entire company.

Collaborating with both internal and external development teams, you will implement and spearhead complex features, including high-speed and scalable multi-tenant runtime environments and sophisticated multi-agent interaction systems. This position is central to building the technical core that enables numerous AI agents to operate and interact seamlessly.

【Responsibilities】

You will be engaged in the development of AI Agents, which serve as the core of the company’s business growth.

・Design and Development of AI Agent Frameworks: Lead the development of core components, primarily utilizing Python.

・Architectural Construction: Build highly scalable architectures that enable seamless coordination and collaboration between multiple AI agents.

・Scalable Runtime Environment: Implement and operate scalable runtime environments for multi-tenant usage, focusing on real-time inference and performance optimization within cloud-native infrastructures.

・Bridge between Research and Production: Collaborate with research teams to define requirements and implement strategies for integrating the latest LLM and AI Agent research into functional products.

・Technical Leadership: Lead technology selection and the improvement of development processes, while providing mentorship to support the professional growth of other engineers.

【Team Structure】

Approximately 65 members are part of the development organization.

Development is divided into the following groups:

・Client-facing Solution Development

・In-house AI SaaS Development

・Common Infrastructure Development (Infra / Data / AI R&D)

【Position/Team Highlights】

・Exposure to Frontier Technology:

You will gain hands-on experience at the absolute forefront of Large Language Models (LLMs) and AI Agents. Working in this hyper-growth sector provides a unique opportunity to drastically accelerate one's technical proficiency and mastery of next-generation AI.

・High Autonomy and Velocity:

Leveraging the rapid decision-making processes characteristic of a high-growth startup, the role offers immense flexibility in adopting and implementing new technologies. It is an environment where your ideas are transformed into reality with remarkable speed.

・Multinational and Diverse Environment:

By working alongside an internationally diverse engineering team, you can deepen their cross-cultural understanding and cultivate a truly global perspective. English-based communication is welcomed, and certain positions are open to candidates regardless of Japanese language proficiency.

・High-Impact Contributions:

You will play a pivotal role in shaping the future of AI-driven products, contributing directly to the success of global clients and entire industries. It is a role that offers a tangible sense of influence over the evolving social infrastructure.

・Accelerated Professional Growth:

Beyond coding, you will contribute to technical strategy and exercise leadership within a high-caliber team. This environment is designed to foster the advanced skills and leadership qualities necessary for the next significant leap in one’s career.

【Development Environment】

・Languages: Python (framework), TypeScript / React / Next.js (frontend) / NX

・Infrastructure: GCP (containers / K8s), Docker

・Tools: Slack, Confluence, Linear, Google Workspace, GitHub, Notion, etc.

・Work Environment: Mac (Apple silicon), dual monitor support

-------------【 Requirements】-------------

【Required】

・Bachelor's degree or equivalent practical experience in computer science, software engineering, artificial intelligence, machine learning, mathematics, physics, or related fields

・Practical experience in application development using Python (5+ years)

・Practical experience in machine learning (3+ years)

- Machine learning algorithms: Fundamental understanding and implementation experience with regression, classification, clustering, etc.

- Data Preprocessing: Skills in data cleaning, transformation, and feature engineering

- Model Evaluation: Understanding and application of evaluation metrics such as accuracy, recall, and F1 score

・Practical experience in Natural Language Processing (3+ years)

- Text Processing Techniques: Experience using NLP libraries (NLTK, spaCy, Transformers, etc.)

- Language models: Experience fine-tuning pre-trained models like BERT, GPT, RoBERTa

・Experience using cloud platforms and container technologies (Docker, Kubernetes)

・Business-level communication skills in English or Japanese (one required)

【Preferred】

・Experience in developing and researching AI/ML, chatbots, generative AI, NLP, agent frameworks, etc.

・Experience with distributed systems and performance optimization in large-scale data environments

・Knowledge of designing and implementing multi-agent systems

・Experience as a team lead or manager, or aspiration toward technical leadership

・Practical experience in a multinational environment

--------------------------------------------------

【Working Hours】

10:00～19:00

【Holidays】

・Saturday/Sunday/National Holiday

・Annual Paid Leave

・New Year Holiday

【Welfare】

【For Full-time Employees】

Housing Allowance: Up to 30,000 JPY/month (applicable to designated areas/stations).

Employee Stock Ownership Plan (ESOP): Opportunity to participate in the company’s growth through stock ownership.

Health & Wellness: Annual periodic health checkups provided.

【For Contract Employees】

Health & Wellness: Annual periodic health checkups provided.

【Common Benefits (Full-time & Contract)】

Learning & Development Support:

・Book Purchase Subsidy: Up to 30,000 JPY per half-year for technical books and learning materials.

・Language & Certification Support: Coverage for Japanese/English learning programs and professional certifications (when required for business).

Work-Life Balance & Wellbeing:

・Monthly Refresh Allowance: Up to 5,000 JPY/month for wellness and entertainment (e.g., gym, yoga, massage, cinema, or theme park tickets).

・Refresh Leave: 2 days of special annual leave granted to employees with over 3 years of continuous service.

Social & Team Building:

・Club Activity Allowance: Up to 5,000 JPY/month to support interest-based internal communities.

・Shuffle Lunch/Dinner: Quarterly subsidies (up to 1,000 JPY for lunch / 5,000 JPY for dinner) to encourage cross-team communication.

Learning & Development (Tech-Specific Support)

The company is committed to providing a cutting-edge environment for creators and engineers.

・AI Tool Support:

Full company coverage for essential AI tools, including Proprietary SaaS services, Cursor, ChatGPT (Plus/Enterprise), Claude, and other industry-standard AI platforms.

・Development Tool Subsidy:

If a preferred development tool or software is paid, the company will cover the cost (up to 30,000 JPY/year).

・Comprehensive Insurance:

Fully equipped with Social Insurance (Health, Pension, Unemployment, and Workers' Compensation).

・Commutation Allowance:

Full coverage of all transportation expenses.

-------------------------------------------------------------------------