Senior Front-end Engineer (React)

About HENNGE

HENNGE is a B2B SaaS company based in Tokyo Japan, and we are at the forefront of the changing workplace. HENNGE One, one of the top cloud security services in Japan, allows customers to adopt flexible work environments and safely harness the power of the cloud from any location. With cloud security ensured, employees are free to focus on working smarter, improving quality, and achieving business results. For further details regarding the engineering teams, products, and more, please visit this link.

Position

We're looking for a senior front-end engineer who thrives in a growth-oriented environment. You will join the Access Control Team, responsible for the HENNGE One Identity Edition, which is part of the HENNGE One suite used by over 2.8 million users across various companies. You will develop and refine core features using TypeScript in React to create seamless user experiences for enterprise clients. We value engineers who are flexible and open to challenges, with opportunities to move between teams through two-way discussions that align with both personal growth and company goals.

Tech stack: 

TypeScript with React, React Router, TailwindCSS (with Class Variance Authority), TanStack Query, TanStack Store, Playwright

Responsibilities:

• Build and improve core front-end features of HENNGE One Identity Edition using TypeScript in React, implementing high-fidelity UI that delivers secure and seamless experiences for enterprise users.
• Take ownership of the full development cycle, from implementation to CI/CD pipelines, testing, and documentation, while continuously improving performance, scalability, and maintainability through modern front-end best practices.
• Collaborate with Design, Product Management, and Customer Success teams to translate ideas and customer feedback into intuitive and polished interfaces.
• Participate in technical discussions and contribute to architectural and product decisions that shape the future of HENNGE One.
• Support teammates through code reviews, knowledge sharing, and open collaboration to foster a culture of continuous learning.

Your qualification

Minimum qualifications:

• 3+ years of professional experience building production-grade web applications using React and TypeScript, with the ability to write type-safe, maintainable code and work with modern React frameworks (e.g., Next.js, Remix, React Router).
• Experience working cross-functionally with PM, UI/UX, QA, and backend teams, and delivering features end-to-end with ownership, including mentoring junior engineers as needed.
• Strong understanding of core frontend application architecture, including complex state management (Redux, Jotai, TanStack Store, etc.), implementing authentication & authorization flows, and integrating APIs using type-safe patterns.
• Ability to write robust tests (unit, integration, E2E) and experience working with CI/CD pipelines.
• Familiarity with performance optimization, secure coding practices, working effectively in very large codebases, accessibility fundamentals, and maintaining good documentation.
• Interest in contributing to open-source projects or participating in the tech community.
• Fluency in English (Japanese is not required), equivalent to CEFR B2 level or above (e.g., TOEIC 785+).

While not required, we'd love to hear if you have:

• Degree in Computer Science or other related technical fields.
• Familiarity working with UI/UX designers and interpreting design specifications (e.g., Figma).
• Experience with observability and analytics tooling (e.g., Sentry, Datadog, New Relic, PostHog, Amplitude).
• Awareness of accessibility and compliance standards (WCAG, security best practices).
• Working knowledge of Unix-like environments and cloud-native development (Docker, Kubernetes, or AWS/Azure/GCP).
• Proficiency with modern React patterns (function components, hooks, server components, and related tooling).
• Team leadership experience.

What we offer

Work style & employment details

Work style
Flexible 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 type
Permanent employee.

Place of work
Tokyo, Japan — Shibuya Headquarters.

Compensation
Annual 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: https://speakerdeck.com/hennge/company-introduction-deck-hennge

Benefits

• English 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 number of days. Details will be provided at the offer meeting.
• Transportation allowance (maximum of JPY 35,000 per month).
• Employee stock ownership plan.
• Insurance: Health, Employment, Industrial Injury, Welfare pension.
• Opportunities to attend international and domestic conferences.
• Financial support for technical certifications and technical learning programs.

Reasons why you will enjoy working at HENNGE:

• We celebrate diversity

  Join a vibrant team from over 20 countries, united by a love for technology and Japanese culture. Located in Shibuya, Tokyo, we offer a dynamic, non-traditional work environment in one of the world's most exciting cities.

• Smooth Japan relocation

  We make your move to Japan smooth and stress-free. We provide comprehensive support such as flight tickets, visa sponsorship, and Japanese lessons, to ensure a smooth onboarding process for our new hires, ensuring a seamless transition and a warm welcome for all candidates.

• Balanced work life

  Work-life balance is highly valued at HENNGE, and lots of fun happens at our office! 200+ of social channels in our Slack, from weekly board game nights to snowboarding club, internal and seasonal events, monthly tech sessions with beer bashes, attendance of international tech conferences, and more. Employees have access to a flexible working hours system (with core working hours) to accommodate their preferred working style.

• Passion for technology

  Our CEO, also serving as CTO, actively leads product development, fostering an environment of innovation and support. Having a leader who truly understands and is still involved in the tech side of the business makes for an exciting and supportive environment for engineers.

• Collaborative teams

  Work in autonomous teams where your decisions shape our services. Influence every aspect of our products, from UX and architecture to development and deployment, in an agile and collaborative setting.

   

  Be part of a diverse and innovative team at HENNGE, where your passion for technology and desire to make a difference are valued and celebrated. Ready to change and challenge the status quo with us?

Additional details

To learn more about life at HENNGE, please check these two links:

• Life at HENNGE
• Stories from our employees

Selection process

1. Solve our coding challenge by clicking the button below. You will receive an email with our guidance upon your submission, and there is no time limit to finish the challenge. Please note that your application will be automatically rejected if:

• you have fewer than three years of professional React experience, and/or
• you complete the coding challenge using a programming language other than React.

2. Once you finish the coding challenge, follow the instructions to upload your CV and Cover Letter. Please check our guide on how to prepare them here.

3. Casual interview with our HR.

4. 2 (or 3) interviews with our engineers (no live coding).

5. Interview with our CEO.

We value your time and want you to perform at your best, so the coding challenge will be the only technical assessment in the process. There will be no live coding sessions.

Have more questions? Please consult our FAQ here.