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Senior C# Developer - Lead Design for High‑Scale Web Systems

Tokyo 23 Wards Temporary ¥6,000,000 - ¥8,000,000 per year Foreign Multinational View Job Description
This senior role focuses on leading design and development for a large‑scale order management platform supporting high‑volume e‑commerce operations. You will contribute to system re‑architecture, cloud migration, and new feature delivery across backend and web applications.
  • Own key design decisions for a mission‑critical platform
  • Join a diverse engineering team driving major system modernization

About Our Client

A major technology‑driven e‑commerce group operating one of Japan's largest online marketplace ecosystems. The engineering division develops and maintains high‑transaction systems and is expanding its global team to strengthen next‑generation platform capabilities.

Job Description

  • Design, propose, and implement new features aligned with business requirements
  • Improve, refactor, and maintain existing functionalities
  • Participate in architectural planning and technical discussions
  • Mentor junior engineers as needed
  • Support system inquiries, troubleshooting, and post‑release operations
  • Work within an Agile/Scrum environment and actively contribute to team practices



The Successful Applicant

Core Fundamentals

  • Strong understanding of IT fundamentals and professional software development practices
  • Solid analytical skills and commitment to writing clean, efficient code
  • Knowledge of web security and personal data protection
  • Experience with high‑transaction, mission‑critical systems
  • Post‑development system operation and maintenance experience

Application Development

  • 5+ years of hands‑on C# development experience, especially WebAPI and SOLID principles
  • Backend expertise with MVC.NET, .NET Framework or .NET Core
  • Experience with .NET 6 or higher
  • Working knowledge of JavaScript/HTML/CSS and REST
  • Experience with Vue.js or another modern JavaScript framework (plus)
  • Cloud design, development, and deployment experience

Database Skills

  • Experience with Entity Framework, Dapper, or similar ORM frameworks
  • Strong T-SQL skills with Microsoft SQL Server

Soft Skills

  • Collaborative, proactive team player
  • Strong communication skills
  • Ability to mentor and coach others
  • Agile mindset and ability to think creatively

Nice to Have

  • Experience with CI/CD tools (TeamCity, Octopus, Jenkins, Kubernetes, Docker, GitHub Actions)
  • Knowledge of messaging systems (Service Bus, RabbitMQ, etc.) and frameworks (Rebus, NServiceBus, MassTransit)
  • Experience with microservices architecture
  • Experience with MariaDB or MySQL
  • Experience with Kafka or other data streaming technologies
  • Experience in Scrum environments or Scrum Master experience
  • Experience working in multicultural teams

What's on Offer

  • Opportunity to drive design and architecture in a large‑scale e‑commerce platform
  • International, diverse engineering environment
  • Growth opportunities and exposure to cloud transformation initiatives
  • Meaningful impact on systems used by millions of users



Contact
Serena Wu
Quote job ref
JN-032026-6977338
Phone number
+81 3 6627 6137

Job summary

Function
IT
Specialisation
Programming / Development
Specialisation
Retail
Location
Tokyo 23 Wards
Job Type
Temporary
Consultant name
Serena Wu
Consultant phone
+81 3 6627 6137
Job Reference
JN-032026-6977338
Company Type
Foreign Multinational

Diversity & Inclusion at Michael Page

We don't just accept difference - we celebrate it. We encourage applicants from all backgrounds to apply for this role and are committed to building inclusive, diverse workplaces where everyone can thrive. If you require any support or reasonable adjustments during the recruitment process, please let us know.