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Backend Engineer - AI for Business Department (AI4B)

Tokyo, Japan💼 Full-time🗓 2026-03-17 → 2026-07-31

Core

Design and operate scalable backend systems and APIs that handle complex AI workloads, integrate with LLM providers, and power intelligent applications for Rakuten's business units.

Role type

Senior IC backend engineer (AI infrastructure)

Builds

Scalable AI application backends, microservices, and event-driven architectures for AI products

Domain

E-commerce, fintech, and digital content; AI/ML infrastructure and backend systems

Deliverable

production ML models | product features

Required skills

Python, FastAPI, PostgreSQL, Redis, microservices architecture, RESTful API design, containerization, TDD, secure authentication, caching strategies

Preferred skills

Multiple LLM provider integration, LangChain, vector databases, embedding management, MLOps, Prometheus, Grafana, distributed systems

Technologies

Python, FastAPI, PostgreSQL, Redis, Azure, GCP, AWS, LangChain, Prometheus, Grafana

Responsibilities

Design and implement high-performance REST APIs and microservices for AI applications; Develop intelligent applications with seamless switching and fallback mechanisms; Build AI service integration layers implementing RAG and agent systems; Implement comprehensive monitoring, security, and testing strategies for production AI systems; Partner with cross-functional teams to translate AI product ideas into production-ready applications

Seniority

Senior, hands-on IC

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