English Speaking Backend Engineer

Role Overview

As a Backend Engineer, you will work on the core systems of our eSIM platform.
This role goes beyond simple API development—you will design, implement, and improve systems that handle payments, inventory, customer data, and integrations with global telecom partners.

We are looking for engineers who can build scalable, reliable backend systems to support our fast-growing global service.

Responsibilities

• Design, develop, and operate backend APIs for mobile apps and web services
• Develop and maintain payment and billing systems
• Design and optimize database schemas and performance
• Build authentication, authorization, and security infrastructure
• Design and operate cloud infrastructure
• Improve development processes through CI/CD, monitoring, and alerting
• Collaborate with frontend and design teams on new features
• Conduct code reviews, select technologies, and promote engineering best practices

Tech Stack

• Mobile App: Flutter
• Frontend: TypeScript (Next.js)
• Backend: TypeScript (Node.js)
• ORM: Sequelize
• Database: MySQL (Cloud SQL)
• Infrastructure: Google Cloud Platform, Firebase
• CI/CD: GitHub Actions
• Design: Figma

Required Qualifications

• 3+ years of experience in web application development using Node.js / TypeScript
• Experience designing and implementing REST APIs
• Experience designing and operating RDBMS (e.g., MySQL)
• Experience developing and operating services on cloud platforms (AWS or GCP)
• Experience with team-based development (GitHub, code reviews, CI/CD)
• Strong product mindset with the ability to see systems from a service-wide perspective

Preferred Qualifications

• Experience designing, refactoring, or scaling service platforms
• Experience with payment, billing, or subscription systems
• Experience integrating with external APIs or telecom systems
• Knowledge of serverless architectures
• Experience with IaC tools such as Docker or Terraform
• Experience leading or mentoring engineers

Language Requirements

• Japanese: Conversational level
  • Equivalent to JLPT N3-4 level or higher
  • Able to handle basic work conversations and chat communication
• English: Fluent

※Internal communication is primarily in Japanese, while English is often used for technical discussions.