【800～1300万円】Backend Engineer AI for Business Department （AI4B）

【求人No NJB2359038】
■Business Overview
Rakuten has launched an agentic AI platform integrated across its ecosystem offering AI chat deep search voice interaction translation coding help and more through Rakuten Link and a standalone web app. The system leverages deep Japanese language and cultural context awareness to deliver highly personalized user experiences. It will be rolled out to Rakuten Ichiba in Autumn 2025 to enhance product recommendations and streamline shopping journeys. Rakuten is also developing Japanese・optimized LLMs including the MoE・based Rakuten AI 2.0 to democratize AI adoption.
　
■Department Overview
Rakuten provides a variety of services in e commerce fintech digital content and communications to users worldwide. Our AI for Business Department operates as a center of excellence focusing on developing and deploying innovative solutions that combine frontier technologies to enhance our products and services across business units.
We are a diverse team of engineers who are passionate about applying their skills to make a significant difference and potentially change society for the better through AI.

Within AI4B our AI Engineering Section serves as the foundation that powers innovation with the mission to design build and scale the technical backbone of our products. Focused on backend systems DevOps practices and cloud infrastructure we ensure reliability performance and adaptability・enabling teams to move fast while maintaining operational excellence. Are you passionate about building scalable high performance AI application backends and APIs・ Join us as a Backend Engineer and help shape the future of AI powered solutions across our ecosystem.

■Position:
As a Backend Engineer you will design and operate scalable systems that handle complex AI workloads integrate with multiple LLM providers and meet strict security latency and reliability requirements across Rakuten's businesses. You'll work with both cutting edge AI technologies and proven solutions like Python FastAPI PostgreSQL and Redis while implementing secure authentication systems comprehensive monitoring and efficient caching strategies.

Your work will involve building intelligent applications leveraging AI designing data models for AI applications including vector storage and embeddings management and developing comprehensive test suites with test driven development （TDD） practices.

This role requires 5+ years of backend development experience with strong expertise in microservices architecture RESTful API design and containerization technologies. You'll collaborate in an international environment requiring strong English communication skills while having the opportunity to work with multiple LLM providers orchestration frameworks and cloud platforms （Azure GCP AWS）. The position offers unique exposure to AI/ML model deployment MLOps practices and real time data processing systems that power intelligent applications used by millions of users worldwide.
　
■Key Job Responsibilities
Design and implement high performance REST APIs microservices and event driven architectures for AI applications
Develop intelligent applications leveraging AI with seamless switching and fallback mechanisms
Build AI service integration layers and implement complex workflows including Retrieval Augmented Generation （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

■Mandatory Qualifications:
Bachelor's degree or above in Computer Science Software Engineering or related technical discipline
5+ years of backend development experience with scalable web applications and APIs
Strong expertise in Python FastAPI PostgreSQL and Redis technologies
Strong English communication skills and experience with collaborative development workflows

■Desired Qualifications:
Experience with multiple LLM providers （OpenAI Anthropic Google Vertex AI） and frameworks like LangChain
Knowledge of vector databases embedding management and cloud platforms （Azure GCP AWS）
Experience with monitoring tools （Prometheus Grafana） and AI/ML model deployment practices
Knowledge and understanding of distributed systems and security best practices