Core Platform Engineer

Job Description

What to Expect

• Work on payment gateway and related backend systems and internal tools.
• Engage with a flat, inclusive, and self-organizing engineering culture.
• Engineers have a direct say in product and technology decisions.
• Substantial ownership and autonomy over your work.
• Opportunities to play to your strengths and invest in new areas for growth.

International Team

• English is the primary language for engineering; many team members are bilingual.
• Optional English and Japanese lessons available for all employees to promote diversity and smooth collaboration across teams.

Position Overview

• Join a small, high-trust team with collaborative and lightweight decision-making.
• Role focuses on backend systems and internal tools, not product or SRE teams.
• Mixture of greenfield development and infrastructure stewardship.
• Work spans backend (Rust, Rails), occasional frontend, infrastructure, and observability.
• Clean abstractions, minimal operational overhead, and pragmatic solutions are highly valued.
• Comfortable learning new technologies as needed.

Responsibilities

• Design, build, and maintain systems and internal tools using Rust and Ruby on Rails.
• Develop and support shared components (CI pipelines, observability tooling, libraries).
• Take ownership of legacy or under-maintained components; improve and stabilize overlooked elements (including occasional frontend or cloud infrastructure work).
• Provide feedback via code reviews and architectural discussions.
• Identify and prioritize high-leverage opportunities for improving team velocity, system clarity, security, performance, and maintainability.
• Champion quality and reliability through automated testing, proactive monitoring, and iterative improvement of production systems.

Requirements

• Production experience with Rust.
• Strong communication skills; able to document technical decisions and collaborate effectively with teams.
• Solid understanding of software architecture, design patterns, and maintainability best practices.
• Practical experience with observability practices (structured logging, metrics, distributed tracing).
• Good grasp of database performance (indexing, query patterns, caching).
• Familiarity with web security risks and mitigation strategies (e.g., injection, CSRF, access control).

Nice to Haves

Not required, but advantageous if you can demonstrate any of the following:

• Experience with: Ruby/Rails, JavaScript/TypeScript, Vue.js, React, Terraform, AWS, or observability tools (Datadog, OpenTelemetry).
• Familiarity with payment systems, payment flows, or financial infrastructure.
• Japanese language ability (reading or conversational).

Multiple openings are available at varying levels of seniority. The final role and responsibilities will be based on experience and interview performance.

Benefits

• Remote work or office space available.
• 10 days regular vacation, plus 5 days each for summer and winter vacation.
• Paid birthday holiday.
• Self-learning allowance and budget for professional development.
• Language training (Japanese).