Senior Frontend Engineer (Svelte) - HENNGE Tadrill

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

Responsibilities

• 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.

Requirements

• 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.

Nice to haves

While not specifically required, tell us if you have any of the following.

• Degree in Computer Science or related technical field.
• 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).

Compensation

¥8,500,000 ~ ¥12,500,000 annually.

Our salary range is inclusive of English Allowance & Physical Communication Bonus - please check the details below, with the final amount determined based on your experience and skills.

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, applicable from October 2025 onwards, 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.