Backend Engineer

Bluefield Energy is an energy-tech startup established in November 2024. This role is part of the Technology Division and contributes to Bluefield Cloud, a platform for managing solar power and batteries, and to related new services in Japan’s electricity industry.

The engineer will work across the service lifecycle, including requirements definition, design, implementation, automated testing, and release of new features. Responsibilities also include improving existing functions, performance tuning, resolving technical debt, improving architecture for scalability and reliability, and building, operating, and optimizing Microsoft Azure cloud infrastructure. The role includes development-process improvement, automation, technical support for team members, and code reviews.

Required qualifications are web application development experience with C# and ASP.NET Core, including REST API design and implementation and use of relational databases such as SQL Server. Experience designing and implementing databases with Entity Framework Core or a similar ORM is required, as is a basic understanding of object-oriented design and design patterns. Experience developing in Azure or another cloud environment, implementing automated tests, working in an agile development process, and communicating in Japanese for team development are also required.

Experience building Azure infrastructure or using Azure DevOps, knowledge of DDD, Clean Architecture, or CQRS, frontend experience such as React, and the ability to keep up with technical information in English are welcomed. The backend stack includes C#, ASP.NET Core, Entity Framework Core, REST with FastEndpoints and MediatR, and xUnit. The frontend uses TypeScript, React with Carbon React, Vite, Vitest, and React Testing Library. Infrastructure includes Microsoft Azure and Azure SQL Database. GitHub Enterprise, Azure DevOps with Azure Boards, Visual Studio 2026 with JetBrains ReSharper, and Microsoft Teams are also used.

The Technology Division has one CTO, two tech leads, and six members. The organization is described as a startup with approximately a dozen people. Company-funded AI tooling includes Claude Code Max (5x) for all engineers, including contractors; Claude Code Max (20x) and OpenAI Codex Pro may also be used when needed. The team is working on measuring and visualizing productivity metrics related to AI adoption and is considering tools such as Findy AI+.

This is a full-time regular position with a three-month probationary period. The annual salary is JPY 6,000,000 to JPY 15,000,000, determined according to experience and skills. The monthly salary is JPY 500,000 to JPY 1,250,000, including fixed overtime pay for 45 hours and fixed late-night allowances for 20 hours; excess overtime or late-night work is paid separately. The workplace is in Shimbashi, Minato-ku, Tokyo. Working hours use a flextime system with no core hours, eight standard hours, and a one-hour break, and start and end times may be set freely. A remote-work system is available.

Holidays include weekends, national holidays, year-end and New Year holidays, and other designated company holidays. Paid leave, maternity and postnatal leave, childcare leave, and nursing-care leave are available. Benefits include a JPY 50,000 welcome payment in the first salary, book-purchase assistance, regular health checks, company housing, commuting expenses, and influenza vaccination. Insurance includes health, employees’ pension, employment, and workers’ accident compensation.