Senior Frontend Engineer

Role overview

We are looking for a Senior Frontend Engineer to lead the frontend development of Tadrill, a specialized platform designed to build organizational resilience by equipping employees to identify and neutralize cyberthreats, especially phishing attacks. As a core component of HENNGE One Cybersecurity Edition serving over 2.8 million users globally, Tadrill transforms employee behavior through continuous, practical attack simulations, automated e-learning, and seamless reporting flows via Gmail and Outlook extensions. In this role, you will architect a high scale and self managed framework, turning complex security data into actionable insights through intuitive dashboards while serving as both a technical owner and a catalyst for team engagement.

While this role primarily focuses on the Cybersecurity 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:

Svelte w/ SvelteKit, Typescript, Playwright, Chromatic, Sentry, Go, AWS

What you’ll do

• Design, build, and ship new frontend features for the Tadrill platform, ensuring a high-quality user experience.
• Monitor, test, and improve the existing codebase to maintain speed and stability as the product scales.
• Collaborate closely with Backend Engineers, Designers, and Product Managers to turn requirements into practical, high-quality code.
• Identify areas for optimization across the entire application lifecycle to improve development efficiency and end-to-end performance.
• Participate actively in code reviews, technical discussions, and documentation to ensure long-term maintainability.
• Mentor junior engineers and contribute to a communicative, connected, and curious team environment.

What we’re looking for

Minimum Qualifications:

• 3+ years of professional experience in frontend development with a strong focus on modern frontend frameworks (Svelte, React, Vue, Solid, Angular etc.)
• Either have used Svelte professionally, in personal projects or have strong interest in working with it.
• Proven track record of maintaining and scaling B2B SaaS products where stability and user-trust are paramount.
• Experience leading technical initiatives or mentoring engineers in a collaborative, cross-functional environment.
• High learning agility: the ability to dive into a specialized domain (Cybersecurity) and master a new stack with speed and curiosity.
• A proactive "owner" mindset: you drive the success of a feature from conception to deployment.
• Fluency in English (Japanese is not required), equivalent to CEFR B2 level or above (e.g., TOEIC 785+); an interest in working within a multicultural environment is essential.
• Interest in contributing to open-source projects or participating in the tech community.

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

• Degree in Computer Science or related technical field.

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• Experience with Go or other backend languages.
• Hands-on experience with cloud infrastructure (AWS, GCP, or Azure) and distributed system concepts.
• Knowledge in Cybersecurity (email security/phishing simulations), especially in the security awareness training domain.
• Experience with Google Workspace or Microsoft 365 integrations, particularly in developing Gmail add-ons and Outlook add-ins.
• Experience in technical project leadership (Team Lead equivalent) or people management (Engineering Manager equivalent).

Work Style and 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.

Remuneration

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

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 has an engineering background and remains deeply engaged in product development. This hands-on understanding of technology helps shape a culture where thoughtful design, technical quality, and continuous improvement are genuinely valued. For engineers, this means working in an environment led by someone who understands the challenges of building products and actively supports teams in doing their best work.

🙌 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?

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. After registering, you will receive an email with our guidance upon your submission. There is no time limit to finish the challenge. Please note that your application will be automatically rejected if you complete the coding challenge using a programming framework other than Svelte.
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.