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Senior C# Developer - Lead Design for High‑Scale Web Systems
| Location | Tokyo - 23 Wards |
| Job Type | Temporary |
| Salary | 6 million yen ~ 8 million yen |
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.
Client Details
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.
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
Job 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
To apply online please click the 'Apply' button below. For a confidential discussion about this role please contact Serena Wu on +81 3 6627 6137.
General Requirements
| Minimum Experience Level | No experience |
| Career Level | Mid Career |
| Minimum English Level | Fluent |
| Minimum Japanese Level | Basic |
| Minimum Education Level | Bachelor's Degree |
| Visa Status | Permission to work in Japan required |
Required Skills
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
- 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
- Experience with Entity Framework, Dapper, or similar ORM frameworks
- Strong T-SQL skills with Microsoft SQL Server
- Collaborative, proactive team player
- Strong communication skills
- Ability to mentor and coach others
- Agile mindset and ability to think creatively
- 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
Job Location
- Tokyo - 23 Wards
Work Conditions
| Job Type | Temporary |
| Salary | 6 million yen ~ 8 million yen |
| Industry | Software |
