Backend Engineer, Ruby

Tokyo
Remote OK - Anywhere in Japan
Full-time
September 19, 2025

About KOMOJU

KOMOJU (by Degica) is 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. Today we help thousands of merchants by providing them with the payment infrastructure they need through developer-friendly API’s to integrations on popular platforms like Shopify and Wix; we help our merchants grow in all markets they are expanding.

What to expect

We are product focused, meaning you will work on our payment gateway and any other projects towards building the future of KOMOJU. You will work with other engineers in a flat and inclusive culture where engineers have a say in both key product and technology decisions. The culture is largely self-organizing, which means engineers have both a stake and ownership in what they work on. Engineers play to their strengths, but are also able to invest in areas where they want to grow within the team. At KOMOJU, you are the main driver behind your growth and position in the company.

International at our core

Most of our engineering team members come from outside Japan. English is the primary language used, and throughout the company, many people are at least bilingual. Being an international company we know the importance of bilingualism. We offer all employees a choice between optional English and Japanese lessons to help create a culture of diversity and ensure smooth collaboration across teams.

About the position

We are looking for a backend engineer to help us build our platform to handle payments on a global scale. You will primarily work with Ruby, building out features using Ruby on Rails (90% of tasks). As we’re still scaling our front-end team, you may be asked occasionally to work on front-end tasks as well (Less than 5% of tasks). As well as this there will be tasks related to Monitoring, Observability etc. which uses Terraform and DataDog (< 5%).

Typical tasks include adding new APIs for Front-end Interfaces in our Ruby on Rails application for customers to use, investigating bugs with our partners to ensure customer payments go through smoothly, and improving our systems’ reliability and observability to ensure better better health using Terraform.

You will work with our product managers and critically evaluate requirements then implement those requirements in code. You will also work with your fellow developers and provide constructive feedback through code reviews, look at refactoring opportunities, and helping improve the codebase. You will receive mentoring support from managers and senior developers to help develop your skills as realizing growth potential is a key goal.

Our ideal candidate has experience working with large web applications. They will know how to build reliable 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

Build backend systems using Ruby on Rails stack.
Understand product goals and feature requests and translate them into working software
Work on large technical projects from design through implementation and delivery as part of a team
Ensure high-quality, reliable software - including thorough testing.

Requirements

You are familiar enough with Ruby to discuss topics such as the Object Hierarchy and meta-programming features such as `method_missing`
Experience with building performant and scalable Ruby applications.
Ability to design data models and system architectures.
Strong technical communication skills - including the ability to document decisions clearly and concisely
Experience and understanding of common web vulnerabilities and how to mitigate them
Understanding of software architecture, design patterns and best practices

Nice to Haves

Experience with TypeScript, Vue.js, or React
Experience with payments or payment systems
Experience with integrating with third party APIs in a secure and fault-tolerant manner
Understanding of database performance characteristics and data access patterns
Familiarity with Monitoring and Observability techniques and platforms such as DataDog.

What is the process like?

We aim to keep our hiring process thoughtful and efficient, typically involving 3-4 stages depending on the role: an initial screening, a take-home exercise, a technical (team) interview, and a final interview with leadership. Throughout the process, the team evaluates candidates not only on technical skills but also on their alignment with team culture and potential for long-term growth. Beyond the Code: How to shine in coding exercises

Benefits

At Degica, we embrace remote work while also offering office space for those who prefer in-person collaboration
10 days regular vacation, additional 5 days summer, and 5 days winter vacation
Paid birthday holiday
Budget for self-learning allowance, to ensure our employees’ skills remain current
Access to the O’Reilly Learning Platform
Language training for Japanese/ English
Twice a week office lunch

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About KOMOJU

KOMOJU (by Degica) is the leading cross-border payment gateway for Japan.

KOMOJU powers payments for leading companies, including the video game distribution platform Steam and the popular mobile app TikTok. Today, the company supports thousands of merchants by providing robust payment infrastructure—ranging from developer-friendly APIs to integrations with widely-used platforms like Shopify and Wix—enabling businesses to scale effectively in new markets.

In terms of engineering, KOMOJU fosters a developer-centric and inclusive culture. The team is committed to continuous improvement through regular self-evaluation and values individuality, recognizing the unique strengths that each engineer brings to the organization.

As KOMOJU grows, its development processes evolve accordingly. The engineering culture is largely self-organizing, with each engineer enjoying significant ownership over their projects. This environment empowers engineers to showcase their strengths while continuing to develop professionally.

Japanese Language Policy
With around half of KOMOJU’s total members (and around 90% of engineers) coming from outside Japan, teams generally use English for written communication(e.g. Slack, Github).

Verbal communication is also primarily in English.

However, quite a few people can speak both English and Japanese fluently, so Japanese may be spoken at times during meetings, especially when they involve teams other than engineering.

Overall, the language spoken depends on the team. The dev team uses mostly English, but the HR team (for example) speaks primarily Japanese.
Visa Sponsorship
KOMOJU sponsors visas for candidates living outside of Japan. KOMOJU also helps out with relocation (searching for apartments etc.) but they don’t have a formal policy for this. The support offered depends on each individual case. They do always pay for flight tickets to Japan in the case that someone moves from abroad.
Paid Leave
KOMOJU offers a generous vacation policy. In line with standard practices in Japan, employees begin with 10 days of paid time off (PTO) in their first year, with the number increasing in subsequent years based on Japanese labor law.

In addition to this, KOMOJU provides 5 extra vacation days during the summer and another 5 days for year-end holidays.

Employees also receive a day of birthday leave each year. Altogether, this adds up to 21 vacation days annually, not including Japanese public holidays. KOMOJU also offers maternity leave, paternity leave, and sick leave.
Benefits
💻 New tech gear

👩‍🎓 Skill development support

💛 Support for attending conferences

📕 Learning Budget

👶 Parental Leave

👩‍🏫 Language Learning Support

💜 Social security / insurance benefits included

🏥 Healthcare insurance

💚 Pension insurance

🚃 Commuter allowance

🛂 Visa and PR sponsorship

👍 Motorized sitting / standing desks when working from the office

🍱 Free office lunch twice a week
Engineer Interview Process
Engineering Roles

KOMOJU aims to keep their hiring process thoughtful and efficient. Typically, it involves 3–4 stages depending on the role:
- Initial Screening
- Take-home Exercise
- Technical Interview (Team Interview)
- Final Interview with Leadership
Throughout the process, the team evaluates technical skills and looks for alignment with team culture and potential for long-term growth.
Work style
KOMOJU operates as a remote-first company while placing a strong emphasis on personal connections and close collaboration. The company maintains an office in the Kichijoji area of Tokyo, which employees are welcome to visit for in-person collaboration and company events, such as weekly lunches provided at no cost.

Team members have the flexibility to work from anywhere within Japan, as well as up to three months per year from abroad. KOMOJU also offers flexible scheduling, allowing employees to set their own hours as long as they are available during the company’s core hours, Monday to Friday from 10:00 to 15:00 JST.