This position is closed and is no longer accepting applications.

Fullstack Engineer

KOMOJU Musashino-Shi, Tokyo May 29 2025
  • 💴 No salary range given
  • 🏡
    Fully remote
    From Japan
  • 🌏
    Apply from abroad
    Relocate to Japan
  • 💬
    No Japanese required
    Business English
  • 🧪
    Intermediate level
    3+ years experience required

About KOMOJU

KOMOJU Musashino-Shi, Tokyo

The leading cross-border payment gateway for Japan. We power payments for companies like video game distribution platform Steam and the popular mobile app TikTok.

Key benefits

  • Developer-centric, inclusive culture
  • International at our core
  • Generous holiday policy

About the position

We are looking for a backend engineer to help up build our platform to handle payments on a global scale. You will primarily work with Ruby, building out features using Ruby on Rails. As we’re still scaling our front-end team, you may be asked to work on front-end tasks as well.

As an engineer you will work collaboratively with the team, to define features and architectures, and then implement them in code. You will also provide constructive feedback through code reviews, as well as architecture discussions.

Our ideal candidate has experience working with large web applications. They will know how to build reliable, scalable, and performant web applications. Testing and code quality are also extremely important to us, so having a strong knowledge of testing and the different testing types is required.

Responsibilities

  • Understand product goals and feature requests and translate them into working software
  • Support team members through code review and architecture discussions
  • Write tests that validate the stability and correctness of implementations
  • Handle refactorings with both bravery and care

Requirements

  • Experience with building performant and scalable APIs, including DB performance
  • Experience with integrating with third party APIs in a secure and fault-tolerant manner
  • Experience and understanding of common web exploits and how to mitigate them
  • Strong understanding of OOP programming languages and patterns
  • Experience with Ruby on Rails

Nice to haves

While not specifically required, tell us if you have any of the following.

  • Experience with TypeScript, Vue.js and/or React
  • Experience with payments or payment systems
  • Business-level spoken and written Japanese

Hiring Process

  1. 1

    Initial screening call with HR

    To understand candidates’ overall professional background, career aspirations, and to evaluate the fit for the role/ culture.

  2. 2

    Take-home exercise

    It’s opportunity to evaluate candidates’ practical experience and observe that they follow best practices.This includes, but is not limited to, their coding skills, problem-solving abilities, system design capabilities and ability to optimize and maintain code. We normally give the applicant one week to complete it, but we don’t expect it to take more than 2 hours.

  3. 3

    Technical team interview

    This interview serves two purposes: it’s a chance to review the take-home exercise and assess the candidate’s technical abilities, and it also helps evaluate their soft skills, how well they collaborate with stakeholders and team members, manage their work (time management, prioritization, adaptability), and demonstrate a commitment to continuous learning.

  4. 4

    Final interview with leadership

    We’re looking here to assess culture add. We’re not looking for people that just fit the status quo (culture fit), we want candidates who can bring something new and valuable to our culture. While ensuring that they still align with our core values, we want to assess their ability to adapt to recent changes within the organization and to help guide the organization through its next stage of development.

Meet KOMOJU's Developers

Kazunori initially joined KOMOJU as a web application engineer, but by identifying problems he wanted to fix, his role shifted first to VP of Infrastructure, and then VP of Payment Products.

Read their story...

Nicole joined KOMOJU in 2020, and worked her way up to be technical lead of the merchant management team. She shares her journey, how KOMOJU supported her career growth and how the company is adapting to its growing needs.

Read their story...
Photo of Richard Ramsden

Becoming CTO of KOMOJU

with Richard Ramsden

After graduating from university, Richard came to Japan and found a job as a software developer. Eventually he joined KOMOJU, where he rose to the role of CTO.

Read their story...

Nigel was fresh out of college when he joined KOMOJU as a developer. He's now risen to tech lead, where he's helped build out their payment platform while maintaining a healthy work-life balance.

Read their story...

Muhammad Denaw, Senior Site Reliability Engineer at Komoju, talks about his work and shares how Komoju's trust and support propelled him to a promotion.

Read their story...

Head of Customer Engineering Makoto Mizukami describes the unconventional candidates his unique team is looking for.

Read their story...

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