Senior Backend Engineer (English Speaker)

Senior Backend Engineer (Remote - Japan/International)

What to Expect

• Work on building and enhancing a payment gateway and related products.
• Collaborate with engineers in an inclusive, flat-structured team with a self-organizing culture.
• Engineers have ownership over their projects and input into product and technology decisions.
• Opportunities to play to your strengths and grow into new areas of interest.
• Growth and personal development are integral parts of your role.

International at Our Core

• Diverse, global team with English as the primary engineering language.
• Optional English and Japanese lessons available for all employees.
• Culture that values and supports bilingualism and collaboration across teams.

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About the Position

Seeking a Senior Backend Engineer to help build a platform capable of handling payments on a global scale.

• Primary tech stack: Ruby, Ruby on Rails.
• Occasional front-end development may be required.

Key Responsibilities

• Build backend systems using Ruby on Rails.
• Translate product goals and feature requests into working software.
• Lead large technical projects: design, implementation, delivery.
• Provide feedback through code reviews and architecture discussions.
• Maintain high-quality, reliable software (testing, monitoring, observability, continuous improvement).
• Identify and execute high-leverage refactoring for maintainability and scalability.
• Mentor junior developers and assist them in improving their core skills.

Requirements

• Experience building large, reliable, scalable, and performant web applications.
• Strong knowledge of testing practices and types.
• Experience building performant, scalable APIs.
• Familiarity with database performance characteristics and data access patterns.
• Ability to design data models and system architectures (OLAP & OLTP).
• Hands-on experience with observability: metrics, logging, tracing.
• Strong technical communication skills—clear documentation of designs/decisions.
• Experience with secure and fault-tolerant third-party API integrations.
• Knowledge of web vulnerabilities and mitigation strategies.
• Deep understanding of software architecture, design patterns, and best practices.

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Nice to Haves

Not required, but valued:

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

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Additional Information

• Multiple openings at various seniority levels (title and responsibilities determined during interview process)
• Remote work supported; office space available for those who prefer in-person collaboration
• Benefits:
  • 10 days regular paid vacation
  • Additional 5 days summer and 5 days winter vacation
  • Paid birthday holiday
  • Budget for self-learning allowance
  • Language training for Japanese