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Software Engineer - Backend (ID Platform)

Mercari Tokyo

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EN: conversational
JP: basic
Employment Type
Full time

Job Description

As Mercari continues to become a rising platform in the market attracting up to approximately 21 million active users, we continue to provide new value to customers on top of what Mercari already offers.

The ID Platform team is a dedicated team that provides the authentication and authorization platform for both marketplace and fintech businesses.

As a software engineer in the ID Platform team, you will support Mercari Group’s growth with not only skills in the backend domain, but also expertise in the authentication and authorization domain.

Team Mission

  • To unleash product and business potential by providing standardized authentication, access control and data protection for all Mercari Products
  • To circulate value by focusing on customer experience and enabling the creation of new value through a standardized ID platform
  • (Learn more about Mercari's mission and values here.)


  • Handle authentication and authorization platform development
  • Providing authentication and authorization-related solutions to teams/projects across the whole Mercari group.
  • API/interface design for microservices using Protocol Buffers and gRPC
  • Improving services and measuring effectiveness using quantitative and qualitative analysis on user behavior logs, etc.
  • Design architecture and select middleware based on application requirements
  • Microservice performance tuning, monitoring, and alert handling

Unique and Bold Challenges

  • You will be able to work on a large-scale authentication and authorization platform that supports the huge customer base for both Mercari. The platform is both internally and externally critical. It will not only support the internal microservices but also be used by our partners for system integration purposes.
  • This platform is built on our own. You will tackle the complex security and user experience problems along with your expert team members.
  • You will dive into the deep ocean of OAuth 2, OpenID Connect, working with your team to renew the legacy authentication feature in a monolithic service by creating new microservices following the OpenID Connect standard
  • During the process of designing and building the platform, you can gain a deep insight into related RFCs and Internet-Drafts
  • You will work in a super diverse team with teammates from more than 8 countries and areas to support other teams who use both Japanese and English


Required Qualifications

  • Shared understanding and belief in Mercari Group mission and values 
  • 5+ years of experience in web application development
  • 3+ years of experience in authentication and authorization development
  • Working knowledge of OAuth 2, and/or OpenID Connect
  • Enthusiasm for solving problems in the authentication and authorization domain
  • Experience designing schemas and creating effective queries for databases (such as RDB, NoSQL, etc.)
  • Experience operating web applications and conducting performance tuning, knowledge of security
  • Experience selecting middleware and designing software architecture
  • Ability to take ownership and lead the software development process

Preferred Requirements

  • Expertise knowledge in OAuth 2, OpenID Connect, WebAuthn/FIDO 2, and other well-known auth schemes.
  • Experience developing and operating using Go, PHP, GCP
  • Experience developing and operating large-scale, high traffic system
  • Experience establishing new services and tackling the challenges in the growth phase of a service
  • Experience as developer lead or management/experience improving the development process
  • Experience in statistical data analysis

Language Requirements

  • English: Independent (CEFR - B2)
  • Japanese: Basic (CEFR - A2) optional

About the Company

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. 

Equal Opportunity Hiring

Here at Mercari, we work to realize a world in which no one’s potential is limited by their background and everyone has the opportunity to freely create value. We also firmly believe that a mindset of Diversity & Inclusion is essential for us to achieve our mission.

This, of course, extends to our hiring practices as well. 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. For more details, please read our D&I Statement.

Employment Status

  • Full-time
  • Probationary period: First 3 months after joining the company. (During this period your contract conditions will be the same as that of a permanent employee.)


  • Roppongi
  • Smoking is prohibited within our offices
  • Mercari has introduced a work style policy called “Your Choice.” Each member is free to choose whether they want to work in the office or work fully remote. *Exceptions made for certain kinds of work.

Work Hours

  • Full flextime (no “core time” or “flex time”)
    *Does not apply to all positions


  • Two days off per week (as well as national holidays, New Year's break, etc.)
  • Paid leave, congratulatory and bereavement leave, relax days, sick leave


  • Annual salary paid in 12 monthly installments (including fixed overtime allowance)
  • Based on skills, experience, and abilities
  • Reviewed twice a year


  • Complete health and social insurance
  • Incentive program
  • Support systems, including those that benefit the employee’s family members
    *See this page for details.


  • Relocation support
  • Language learning support
  • Translation/interpretation support