Senior Frontend Engineer

Thesirius; San Francisco, Northern (CA, KY); Hybrid; USD 100,000 - 150,000; Full time

Benefits offered by this job

In-person, in SF

Flexible healthcare

Ownership of what you build

Lunch, coffee & snacks

Time off

Company events

Job summary

Thesirius in San Francisco is seeking a Frontend Engineer to design, develop, and maintain user-facing components of our core products. You will collaborate with backend, product, and design teams to deliver high-quality integrated solutions.

You will drive adoption of modern frontend technologies, tackle performance and UX challenges, and contribute to a culture of engineering excellence. This is an in-person, on-site role in San Francisco with visa sponsorship not available.

Qualifications

• 1+ year of frontend development experience for production apps.
• Strong proficiency in JavaScript/TypeScript and modern frontend frameworks.
• Experience integrating frontend apps with backend APIs and third-party services.
• Solid understanding of UI/UX, performance, and frontend architecture.
• Ability to drive projects to completion independently.
• Based in San Francisco or able to relocate/be onsite full-time. Visa sponsorship not offered.

Responsibilities

• Architect and build robust, scalable, user-friendly interfaces.
• Collaborate with backend engineers, product, and design teams to deliver integrated solutions.
• Drive adoption of modern frontend technologies and practices.
• Identify and resolve performance, UX, and security challenges.
• Contribute to a culture of continuous improvement and engineering excellence.

Skills

Frontend development

JavaScript/TypeScript

Frontend frameworks

APIs integration

UI/UX

Project ownership

Job description

About Us:

We’re on a mission to make subscriber churn a solved problem. Backed by a16z Speedrun, we build AI agents that help consumer subscription brands — like Higgsfield and Promova — retain more users, extend lifetime value, and grow fast. We’re an incredibly driven team working on a problem that affects every consumer on the planet. If that sounds like your kind of thing, we’d love to meet you.

Our co-founders are Azamat Khamidov and Benazir Toleubekova. Azamat built a Telegram AI product from zero to five million users in four months, the first acquisition inside Telegram. Benazir received a full scholarship to Beijing University of Technology at 15. Joined Taobao at 17. At Alibaba, architected the core recommendation engine serving 500M daily users.

What You’ll Do:

As a Frontend Engineer, you will play a key role in designing, developing, and maintaining the user-facing components of our core products. Your responsibilities will include:

• Architecting and building robust, scalable, and user-friendly interfaces to support new product features and evolving business needs.

• Collaborating effectively with backend engineering, product, and design teams to deliver high-quality integrated solutions.

• Driving the adoption of modern frontend technologies, frameworks, and methodologies to ensure product quality and maintainability.

• Identifying and resolving complex technical challenges related to user experience, performance, and security.

• Contributing to a culture of continuous improvement and operational excellence within the engineering team.

What You’ll Bring:

• +1 year of professional experience in frontend development for production-level applications.

• Advanced proficiency in JavaScript/TypeScript and modern frontend frameworks

• Demonstrated experience integrating frontend applications with backend APIs and third-party platforms.

• Solid understanding of UI/UX principles, performance optimization, and frontend architecture.

• Strong analytical skills and the ability to independently drive projects to completion.

• Based in San Francisco or able to be here full-time. We’re not offering visa sponsorship at this time.

Our Values:

Stewardship: We build for the long term. Every customer, partner, and teammate gets that same commitment from day one.

Trust: Earned through the integrity of our technology, the consistency of our commitments, and the honesty of our communication.

Customer Obsession: We win when our customers win. Every choice and conversation orbits around what makes them stronger.

Excellence: The same standard for the product we ship, the service we give, and the team we build. The bar is the bar.

Family: A constellation, not a single star. We back each other on hard days, celebrate the great ones, and protect the time teammates need to be parents, partners, and humans first.

Life at Sirius:

In-person, in San Francisco: We work side by side, on-site in San Francisco. Proximity helps us move faster, solve harder problems, and build something we’re proud of together. Note: we’re not able to offer visa sponsorship at this time.

Flexible healthcare: We offer flexible spending to direct your benefits toward what matters most to you and your family.

Own what you build: We’re building something real, and we want you to own it.

Lunch, coffee & snacks: Daily lunch, plus coffee, tea, and snacks to keep you going.

Time off that’s actually off: Take the time you need to show up as your best self. We mean it.

Company Events: Take the time you need to show up as your best self. We mean it.