Senior Software Engineer, Agentic AI Platform - Mercari

JD in Japanese follows. 英文の後に和文JDをご覧いただけます。 Senior Software Engineer, Agentic AI Platform - Mercari Employment Status:　Full-time  Work Hours: Full Flextime (no core time)   Office: Roppongi For more details, see the Overview of Our Positions section on our Careers site. About Mercari Circulate all forms of value to unleash the potential in all people "What can I do to help society thrive with the finite resources we have?" The Mercari marketplace app was born in 2013 out of this thought by our founder Shintaro Yamada as he traveled the world.

We believe that by circulating all forms of value, not just physical things and money, we can create opportunities for anyone to realize their dreams and contribute to society and the people around them. Mercari aims to use technology to connect people all over the world and create a world where anyone can unleash their potential. For more information about Mercari Group’s mission, see Mercari’s Culture Doc Organization/Team Mission Mercari Engineering Principles   Mercari Engineering Principles are a shared understanding that serves as the foundation of engineering beliefs and behavior at Mercari.

The Engineering Principles are designed to complement the organizational identity (Mercari’s mission, values, and culture) from an engineering viewpoint.  These principles ultimately help us achieve Mercari’s mission by defining the ideal state we seek to realize in the long term.  Passion For The Product Grow Together Solve Through Mechanisms Collaborate Openly For more details, please see the following link: Engineering Culture The AI Platform team drives Mercari Group's transformation into an "AI-Native company" from the perspective of technical foundations.

We design, develop, and operate shared AI infrastructure used across the company, including an LLM Gateway, MCP Gateway, and Agent Sandbox, and we also build the AI Agents that work alongside development and operations on the ground. What we build is used in two ways. First, as services that every role—including engineers, designers, and PMs—uses directly in their daily work. Second, as shared building blocks that other engineering teams inside Mercari use to construct AI workflows tailored to their own domains.

For the former, we create an environment where every role can demonstrate AI as a baseline skill, through developing AI Agents and running PoCs for AI SaaS. For the latter, we provide foundations with enough generality for other teams to extend on their own, and enough reliability for them to trust with real work. Where a product team delivers customer value directly, we make other teams able to deliver that same value themselves.

That is why we measure ourselves not by the number of things we have built, but by what the people using them became able to do. In this role, you will work as an enabler for AI-native development across Mercari Group while owning the shared AI platform it runs on: you build the mechanisms that let other teams work AI-natively, and you operate the production services those mechanisms depend on. See here for more information about our mission and values.

Work Responsibilities You will be responsible for designing, developing, and operating the technical foundations that enable AI adoption across Mercari Group. Design, develop, and operate the AI Platform: Design, implement, and operate shared AI infrastructure such as the LLM Gateway, MCP Gateway, and Agent Sandbox. These are production services the whole company depends on, so you own their operation—availability, security, and cost optimization—alongside the enablement work.

Decide what to offer as company-wide infrastructure by weighing the range of teams affected, the impact on development as a whole, and system-wide risk. Build AI Agents and an execution platform: Develop AI Agents that work alongside development and operations, and build an execution platform that shifts the developer experience toward AI-nati