Software Engineer — Fraud Prevention
What to Expect
You will work on our payment gateway and related projects focused on building the future of payments. The team operates with a flat and inclusive culture, allowing engineers to participate in key product and technology decisions. The environment is self-organizing: engineers have ownership over their work, play to their strengths, and are empowered to grow in new areas. You will drive your own growth and progression.
International at Our Core
The engineering team is globally diverse, with English as the main working language. Employees can choose from optional English or Japanese lessons to foster a collaborative and inclusive culture.
About the Fraud Prevention Team
This team is the frontline defense against payment fraud, protecting merchants and customers worldwide. It builds and maintains intelligent systems for real-time fraud detection and analysis, utilizing Ruby, Python for machine learning models, OpenRouter for LLM integrations, and OpenTelemetry for observability.
Impacts You’ll Bring
As part of the Fraud Prevention Team, you will:
- Design, build, and maintain software for fraud prevention.
- Develop robust antifraud solutions and merchant-facing features for transaction visibility.
- Help scale systems to manage increased complexity and demand.
- Combine engineering best practices with advanced fraud prevention to safeguard large transaction volumes.
Key Responsibilities
- Implement antifraud solutions and improve system robustness.
- Develop merchant-facing risk management tools: dashboards with real-time fraud insights, customizable rules, and actionable data.
- Translate ML models (e.g., merchant risk scorecards) into production-ready code.
- Work autonomously and deliver impactful features with minimal meetings.
- Debug complex production issues and integrate smoothly into the existing codebase.
- Demonstrate ownership and drive projects independently.
- Communicate complex technical concepts to various stakeholders.
- Be a detail-oriented team player, catching edge cases and supporting team coverage.
Requirements
- 5+ years professional experience as an engineer (current or senior level).
- At least 2 years of personal or professional experience with Ruby.
- Expertise in production debugging.
- Strong sense of ownership and self-driven project management.
- Excellent communication and team collaboration skills.
- Business-level English proficiency.
Nice to Haves
Not required, but highly valued:
- Experience with statistical methods (logistic regression, GLMs), machine learning, EDA, data ETL pipelines, and SQL for data analysis.
- Knowledge of Python or other major programming languages.
- Payment industry or credit card system experience.
- Background in payment security or broader security systems.
- Conversational-level Japanese proficiency.
Tech Stack
- Backend: Ruby on Rails, Python (Django), MySQL, PostgreSQL, RedShift
- Frontend: React, Vue.js, Webpack, Storybook
- Infrastructure: AWS, Terraform, Docker
- Data & ML: GLM, Logistic Regression
Hiring Process
The hiring process typically includes 3–4 stages:
- Initial screening
- Take-home technical exercise
- Technical/team interview
- Final interview with leadership
The process evaluates both technical skills and cultural alignment. Tips for coding exercises
Benefits
- Remote work flexibility, with office space available
- 10 days of regular vacation, plus 5 days each for summer and winter holidays
- Paid birthday holiday
- Budget for self-learning and personal development
- Language training for Japanese
- O'Reilly company membership
- Office lunch twice a week