Principal Backend Engineer (Python, AI)

TOP 3 REASONS TO JOIN US

• Perks you will love: Hybrid woring; 16 - 24 paid days off; Top modern & sufficient devices
• Solid global business: No.1 market - 13.7 million B2C users in Japan; 140,000+ paying business customers; Listed in the prime market of Tokyo Stock Exchange
• Hub of growth support: Fintech industry; Tailored L&D programs for individual growth

Job Description

We are looking for a backend engineer to lead the development of our AI Agent platform/application from the ground up. The ideal candidate has experience designing scalable systems, integrating with complex toolchains, and driving cross-functional teams with strong technical leadership.

Responsibilities

• Lead backend development of the AI Agent platform or application from scratch, handling large-scale user data and system logs

• Design and build complex system architectures that integrate with internal/external APIs, vector databases, and various developer toolchains

• Monitor system behavior proactively and respond swiftly to abnormal agent behavior or system failures

• Introduce tools, systems, and development culture to improve engineering efficiency and team collaboration

• Mentor and support the growth of team members by helping them develop strong technical fundamentals

• Take technical leadership across a cross-functional team—including backend, frontend, AI, and SRE engineers—and drive the overall development process

Requirements

• Technical

  • Must have

    • 5+ years for Web development

    • 3+ years of experience with Python (or Golang as an alternative)

    • Solid understanding of:

      • Frontend development (e.g., TypeScript, React)

      • Cloud infrastructure (e.g., AWS, Azure, Terraform, serverless architecture)

      • AI system integration (e.g., working with LLM APIs, embedding, vector DBs

    • Experience with:

      • Type hinting and static analysis using mypy

      • Unit testing using pytest

      • Code quality tools: black, flake8, isort, bandit

      • Docker and containerized development

      • Operating and maintaining applications in a production environment

      • Application performance tuning

      • Agile development processes

  • Nice to have

    • Experience with:

      • Django (web framework)

      • Celery (asynchronous task processing with Amazon SQS or other brokers)

      • Graphene (GraphQL library with code-first approach)

    • Practical knowledge in:

      • Container Orchestration (e.g., Kubernetes, Kustomize)

      • Frontend architecture design or collaboration with frontend engineers

      • Integrating LLMs into production applications (e.g., prompt management, RAG pipeline, evaluation tools)

      • Infrastructure as Code (IaC) and CI/CD pipeline automation

      • Experience in B2B application development

• Communication

  • Experience leading a project as a team lead (required for Leader position)

  • Experience mentoring or educating team members

  • Strong sense of ownership and accountability