Product Engineer Backend, Global Supply - Mercari

Minato City, Tokyo, Japan – Hybrid / Full-time

Description

Employment type: Full-time employee
Work style: Flextime (no core hours)
Location: Roppongi

Organization / Team Mission

In the Marketplace business, we aim to realize a global marketplace that creates new value—driving the growth of diverse businesses through the creation of customer value. Starting with the operation of Mercari, Japan's largest flea-market service, we advance the Mercari Group's mission through our cross-border business and various new ventures.

We’re building a single commerce foundation shared across all Mercari marketplaces, rather than separate foundations for each business and country.

As part of the team, your mission will be to realize our global marketplace—enabling both individual sellers and businesses to list items that customers worldwide can buy with ease and confidence.

Under a development structure that assumes AI, we pursue both the delivery of customer value and maximum speed at the same time. Engineers in this position are expected to act as Product Engineers (PdE), taking end-to-end responsibility from specification through the completion of delivery. You will not be confined to your own area of expertise, and are expected to cross boundaries in order to solve problems. From the Definition phase onward, you'll take the initiative and autonomously lead specification concretization, alignment, quality and measurement, release, and the operations that follow.

Mercari Engineering Principles

• Passion For The Product
• Grow Together
• Solve Through Mechanisms
• Collaborate Openly

Responsibilities

As a Product Engineer (PdE), you will take end-to-end accountability for Global Supply — from shaping specifications through production release and the operations that follow — working closely with a Product Manager and other stakeholders.

Across all of this, you'll be building for more than the first market — from how items get listed to how customers worldwide reach them, what you ship should hold up for the next country without being rewritten.

Key Responsibilities

1. Drive specification and implementation for foundational capabilities
   Start from working prototypes: use running code to settle open questions and finalize specifications, and lead implementation across services and platforms

2. Own quality, measurement, and release across markets
   Establish measurement (events, logs, dashboards), quality bars, and phased rollout plans, and carry changes through production release and the operations that follow

3. Make architecture decisions that outlive the feature
   Decide what belongs in the shared foundation versus what stays specific to a market, and when to extend what exists versus build new

Examples of Tools Used on the Job

• A range of tools centered on Claude are available
• We expand and change the models and tools we offer on an ongoing basis, in line with requests and industry trends

Unique Challenges

• Mercari's marketplace grew up in Japan, and much of what powers it today was built for Japan. This area is about shaping the foundation for a genuinely global marketplace — one designed from the start for multiple markets, languages, currencies, and regulatory environments rather than retrofitted for them. That runs all the way down to how listing itself works: it has to stay effortless for someone selling a single item, work just as well for a business listing at scale through an API, and still produce data structured enough to power search, pricing, and recommendations in every market.
• Global demand is growing faster than the supply available to serve it, which puts this area directly on the critical path for growth. There is a short and visible line between what you ship and how much selection customers around the world can actually reach — and the foundation underneath it doesn't stop at supply.
• Much of this is still undecided: where the boundary sits between what's shared globally and what stays specific to a market, what to build new versus what to carry forward, and which problems to solve first. We're also asking what changes when AI agents, not just people, are listing and buying. You'll be part of deciding, not handed the answers.

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Requirements

Required experience / skills

• You resonate with the mission and values of the Mercari Group and of each company
• Ability to lead not just implementation but specification concretization and stakeholder alignment, taking end-to-end responsibility through production release and the operations phase that follows
• Practical AI-assisted development ability
• Use AI coding tools (e.g., Claude Code/Cursor/Copilot) in real work and can judge, correct, and integrate AI outputs safely
• Can prototype fast and iterate behavior/requirements using working code as a discussion artifact
• Autonomous technical design judgment (architecture/API/data/security/operations) and ability to explain trade-offs in business context
• Cross-layer learning agility (BE/FE/iOS/Android/QA etc.) and willingness to cross into adjacent job functions: does not draw hard boundaries like “I only do X”, and can get up to speed in unfamiliar areas using AI and documentation
• Willingness to mentor and coach the people around you, with motivation for the growth of the organization

Preferred experience / skills

• Experience building or migrating systems that serve more than one country, currency, or regulatory environment
• Experience extracting shared capabilities out of a system originally built for a single market
• Experience designing APIs or data models consumed by teams you don't control
• Experience operating what you built after launch — on-call, incident response, or long-term ownership
• Experience collaborating with Product Managers as a peer to drive alignment and unblock decisions
• Knowledge of C2C/B2C marketplaces, commerce, logistics, or cross-border domains

Language

• English: Proficient (CEFR B2) or above required
• Japanese: Nice to have

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About the selection process

At the Mercari Group, we value resonance with and embodiment of our mission and values. To build an organization that maximizes the total value our members create, we want to accurately understand each candidate's experience and skills.

Selection flow

• Document screening
• Skill test
• Interviews: multiple rounds depending on the position
• Reference check: online response format (conducted around the final interview)
• Offer: decided based on the results of the final interview and the reference check

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Equal Opportunity

At Mercari, we aim to realize a society in which an individual's potential is not predetermined by their background and everyone has the opportunity to freely create value. We believe that "Inclusion & Diversity" is indispensable to realizing our mission.

In our hiring activities as well, so that people of diverse backgrounds who resonate with Mercari's mission and values can join us, we promise to eliminate all discrimination based on age, gender, sexual orientation, race, religion, physical ability, or any other attribute.

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