Senior Software Engineer (Backend/Infrastructure) [Relocation to Tokyo Required]

RolesWe are looking for a Senior Software Engineer to take ownership of backend and web-platform development for HENNGE One, our flagship cloud-security suite serving over 2.8 million users globally. As a B2B SaaS leader in Japan, we provide mission-critical security solutions that empower enterprises to work safely from anywhere. In this role, you will join the Secure Transfer Team, responsible for the development of HENNGE One Data Loss Prevention (DLP) Edition.

You will be developing our high-security file exchange solution—the "Secure Vault" of our ecosystem. Your mission is to architect the fault-tolerant, high-availability systems required to handle and protect sensitive enterprise data. This position is ideal for engineers who want to bridge the gap between advanced backend development and deep cloud infrastructure, utilizing tools like Kubernetes and Terraform to ensure data integrity.

While this role primarily focuses on the DLP Edition, we value engineers who are flexible and open to new challenges, with opportunities to move between teams and products through two-way discussions that support your growth and the company’s goals.

Tech Stack: FastAPI, ArgoCD, PostgreSQL, AWSWhat you'll doDesign, build, and maintain new features for HENNGE One, using Python and other web technologies.Architect scalable, fault-tolerant services deployed in cloud environments.Automate deployment, testing, monitoring and documentation via CI/CD pipelines and infrastructure-as-code.Collaborate closely with Product Management, Design, and Customer Success teams to deliver high-quality user experiences.Participate actively in code reviews, discussions and technical decision-making.Mentor junior engineers, and contribute to improving team processes and engineering culture.

What we're looking forMinimum Qualifications3+ years of experience developing production-scale web applications using Python.Strong experience across the software development lifecycle (SDLC), from system design to deployment and maintenance.Hands-on experience with containerization and orchestration technologies (e.g., Kubernetes, ArgoCD).Experience with Infrastructure-as-Code tools, such as Terraform.Deep expertise in architecting and operating mission-critical AWS environments.Experience with CI/CD, automated testing, code documentation, and clean-code practices.Ability to lead technical initiatives, mentor junior engineers, and work collaboratively in a team environment.Fluency in English (Japanese is not required), equivalent to CEFR B2 level or above (e.g., TOEIC 785+).Interest in contributing to open-source projects or participating in the tech community.

While not required, we'd love to hear if you haveDegree in Computer Science or other related technical fields.Experience building large-scale distributed systems or SaaS products in the B2B space.Familiarity of Go, or a strong interest in learning it, to help build and maintain our multi-language backend infrastructure.Additional experience with cloud security best practices, including PII obfuscation and secure data-handling protocols.

Work Style and Employment DetailsWork StyleFlexible working hours with a designated core time (11:00-16:00), allowing you to organize your day effectively. Employees typically work 8 hours per day with a 1-hour break. Employment TypePermanent employee. Place of WorkTokyo, Japan — Shibuya Headquarters.

RemunerationAnnual salary: JPY 8.5M to 12.5M (includes English Allowance and Physical Communication Bonus)Please refer to our Company Introduction Deck for an explanation of our Assessment System and the Belt System, which we use to determine the candidate's salary range BenefitsEnglish Allowance and Advanced Language Expert Allowance: JPY 10,000 ~ JPY 130,000 per month, paid alongside base salary, if the employee fulfills the requirements.Physical Communication Bonus: JPY 4,000 per day* for coming to the office and interacting with other employees, paid out as bonus according to the num