シニア・フルスタック・ソフトウェアエンジニア

Build the Digital Infrastructure for Battery Manufacturing💻

About the Company:

Beff is a global Technology partner for Battery Development, mass production, and Data Management.

Job Description:

We’re building a high-impact SaaS platform at the intersection of Battery Design, Development, and Production, and software, focused on solving real-world problems in the battery ecosystem.We’re looking for a Senior Full-stack Software Engineer to take ownership of our web applications - from architecture to production. You’ll work on systems that ingest, process, and serve complex data, and help shape a platform that customers rely on for critical decision-making.This is a high-ownership, hands-on role for someone who thrives in ambiguity, makes strong technical decisions, and ships reliable systems quickly without sacrificing quality.Experience in the battery sector is a strong plus.

Job Responsibilities:

• Architect solutions that are maintainable, extensible, and clean
• Build high-quality, modular, and performant UIs using React.js and any other most suitable tools.
• Own API design and service architecture, balancing performance, maintainability, and developer experience
• Build and maintain multi-service, cloud-native systems on AWS
• Improve system observability, reliability, and incident response practices
• Drive CI/CD, infrastructure-as-code (Terraform), and secure deployment workflows
• Make pragmatic decisions - knowing when to move fast and when to invest in long-term architecture
• Contribute to a culture of high-quality engineering through code reviews, testing, and continuous improvement

What We’re Looking ForCore Requirements

• 5+ years of experience building and operating production backend systems
• Strong proficiency in Python(FastAPI), Nest.js, React, Typescript, Tailwind, PostgreSQL, and frontend fundamentals (performance, accessibility, usability)
• Proven track record of building and maintaining real-world applications
• Startup-ready: you’re comfortable wearing multiple hats, working fast, and owning outcomes.
• Clear understanding of product tradeoffs and agile product development
• Strong communication skills - you ask questions, raise flags, and explain your thinking
• Deep understanding of:
• API design (REST, service boundaries, versioning)
• Distributed systems and microservices tradeoffs
• Data modeling and database performance
• Hands-on experience with:
• AWS (or similar cloud platforms)
• Docker and containerized environments
• CI/CD pipelines and infrastructure-as-code
• Japanese: Business Level
• English: Business Level

Strong Plus:

• Experience in the battery domain
• Experience building data-intensive or real-time systems
• Experience designing event-driven architectures

Tech Stack:

• Backend: Node.js (Nest.js), Python (FastAPI)
• Frontend: React.js (Hooks, Context, modern state management, component libraries)
• Databases: PostgreSQL, Redis, NoSQL
• Infrastructure: AWS, Docker, Terraform, GitHub Actions

Why Join Us?

• Work on real-world energy problems with tangible impact
• Own systems end-to-end
• Influence architecture, product, and technical direction
• Build from first principles in a fast, execution-focused team
• High autonomy, low bureaucracy, and meaningful responsibility

Salary

Negotiable

Note:

When applying, please provide details of the projects you have worked on, including the tools and technologies you used, your role and responsibilities, and the measurable results or business impact you delivered.