Product Engineer (Backend) - Mercari Marketplace New Business Engineering

Description

Employment Type: Full-time
Work Hours: Flextime system (no core hours)
Office: Roppongi, Minato City, Tokyo, Japan
Hybrid / Full time

This team builds emerging marketplace domains that will become Mercari’s next growth pillars, including cross-border and new commerce experiences. You will collaborate across Mercari and/or with external partners to turn early hypotheses into scalable products—leveraging the strengths of our existing marketplace while laying the foundation for the next stage of global growth and enabling a safe, global marketplace where sellers and buyers worldwide can transact with confidence.

Under a development structure built around AI, we aim to maximize both the value we deliver to users and the speed at which we deliver it. As a Product Engineer at Mercari, you will take end-to-end ownership from spec definition through delivery. We are looking for someone willing to go beyond their role to solve problems, rather than staying confined to their own area of expertise. You will be expected to proactively get involved from the definition phase, and to independently lead every step of the development process—shaping product specs, building consensus, establishing quality and measurement, releasing, and the operations that follow.

Main Responsibilities

• Leading spec definition and implementation
  Start from a working prototype rather than waiting for perfect specs: build something first, then update and finalize the specs based on observed behavior, and lead implementation across platforms.

• Leading quality, measurement, and release phases
  Establish reliable measurement through event design, logging, and dashboards, while also designing quality standards and phased rollout plans.

• Making technical design decisions autonomously
  Independently make decisions on architecture, APIs, data design, security, and operational considerations, explaining trade-offs in a business context to drive progress.

Tools and Technologies Used

• Access to a range of tools centered around Claude.
• Regularly expand and update our selection of models and tools in line with team needs and industry trends.
• For more information, see the Technology Stack page of our Engineering portal.

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Qualifications

Required Experience/Skills

• Shared belief in the mission and values of Mercari Group and its various companies
• Ability to take end-to-end ownership: personally leading not just implementation, but spec definition and consensus-building, and staying accountable through production release and maintenance
• Ability to leverage AI in development while balancing speed and quality
• Ability to use AI coding tools like Claude Code effectively in day-to-day work, while evaluating, correcting, and integrating AI output rather than taking it at face value
• Ability to build prototypes quickly and finalize specs based on these working prototypes
• Ability to make technical design decisions autonomously (architecture, APIs, data, security, operations, etc.) and explain trade-offs in a business context
• Willingness to cross into other domains (backend, frontend, iOS, Android, QA, etc.) and adjacent roles, with the ability to get started on your own in unfamiliar areas by leveraging AI and documentation
• Willingness to mentor and coach others with a motivation to help the organization grow

Preferred Experience/Skills

• Experience delivering results from ambiguous specs: prototyping, refining and finalizing the specs, and seeing the project through to delivery
• Experience with measurement design (events/logs), dashboard development, phased rollouts, and making go/no-go release decisions
• Experience working alongside product managers to finalize specs, unblocking decisions when they get stuck
• [FILL IN: Add any other preferred experience/skills in the relevant domain (C2C Marketplace, Commerce, Logistics, Fintech, etc.)]
• Experience using English professionally, or experience developing products in a multinational team

Language Requirements

• Japanese: Proficient (CEFR - B2) required
• English: Independent (CEFR - B1) preferred
  • For details about CEFR, see the Language page of our Careers site.

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Selection Process

• Document screening
• Skills test
• Interviews: multiple rounds, depending on the position
• Reference check: completed online (conducted before or after the final interview)
• Offer: decided based on the results of the final interview and reference check

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Equal Opportunity Hiring

Mercari is committed to eliminating discrimination based on age, gender, sexual orientation, race, religion, physical disability, and other such factors so that anyone who shares our mission and values can join us, regardless of their background.

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