We are currently building a new product from the ground up that centers around AI Agents, delivering a radically new user experience.
This product is being built from scratch, and the backend plays a critical role in orchestrating LLMs, tools (MCP), custom workflows, agent’s long/short term memory, and user data with reliability and flexibility.
To succeed, we need backend engineers who are not only technically strong but also product-minded and eager to tackle ambitious challenges alongside a cross-functional team.
Responsibilities
- Design and develop backend systems using Python and Go for a new AI Agent product from the ground up
- Implement APIs that interface with agent engine, managing session storage, message queues, database and other backend components, ensuring robustness of task execution, and designing data models that reflect real-world agent behavior.
- Integrate external tools and internal components (LLMs, workflow engines, etc.)
- Ensure reliability, observability, performance, and scalability in production environments
- As an early team member, you’ll also be deeply involved in architecture design, technology selection, and team culture. This is not a “build to spec” role—you’ll collaborate closely with designers, product managers, and AI engineers to iterate quickly and deliver user-impactful features.
- Contribute to automation, testing, documentation, and engineering process improvement
- Mentor junior engineers and contribute to team growth
Requirements
- 3+ years of professional experience in backend development for web applications
- Proficiency in programming languages such as Python, TypeScript, or Go
- Experience designing and implementing APIs (e.g., REST, WebSocket)
- Experience in designing and operating databases such as PostgreSQL, MySQL, or MongoDB
- Basic knowledge of microservices, distributed systems, and asynchronous processing
- Ability to work autonomously in collaboration with cross-functional roles such as product managers, designers, and AI engineers
- Japanese language proficiency equivalent to JLPT N2 or above
- Interviews will be conducted in Japanese
- Only the first interview (Coding & System Design) can optionally be conducted in English
Nice to haves
While not specifically required, tell us if you have any of the following.
- Foundational understanding of LLMs or AI Agents, or experience developing related products
- Experience in session management, job scheduling, and queue processing (e.g., Redis, Kafka, SQS)
- Knowledge of infrastructure tools such as Docker and Kubernetes
- Experience with CI/CD pipelines, test automation, and observability/monitoring tools
- Experience in designing and reviewing systems with a focus on security and scalability
- Hands-on experience in early-stage startups or new business development environments
- Strong communication skills, with the ability to work effectively across diverse cultures in both English and Japanese
Compensation
¥7,700,000 ~ ¥12,000,000 annually.
