As the Founding Frontend Engineer, you will own the “backend of the frontend” for a million-line React codebase. You’ll architect high-performance SSR systems, scale state management, and build agent-ready UI infrastructure. This is a high-ownership role for a specialist-generalist who values velocity, product taste, and defining the future of music.
Founding Frontend Engineer at Mozart AI
Mozart AI is seeking a Founding Frontend Engineer in London to lead the "backend of the frontend" for a social music revolution. Backed by $7M+ from Balderton Capital and industry legends like Kevin Hartz, we are building an effortless music creation experience for a global audience. You will own the architecture of a 1M+ line React codebase, scaling SSR systems and building agent-ready UI infrastructure. This role is perfect for a specialist-generalist who uses AI as their primary driver to ship fast and high-quality code. Join us to shape the future of music through high-performance engineering and founding-team equity.
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Location
London, United Kingdom
Compensation
Not Disclosed
Company
Mozart AI
Role overview
Software10 employeesLondon, United KingdomPre-Seed (VC-backed)
Mozart is building a world where everyone can feel the joy of creating music, socially. Our customers range from grandmas using Vibe sessions to Grammy winners using the Studio. Music is entering its first explosive moment of creation-driven consumption, and we want to shape that world while preserving the social, fun side of music creation. We’ve raised over $7m from Balderton Capital (backers of Revolut) and Silicon Valley legends like Kevin Hartz, Emery Wells, backers of Uber, Spotify, etc.
Backed by EWOR, New Renaissance Ventures, Atlantis Ventures, Felix Jahn, Stefan Glaenzer.
What you will do
- Master the 1M+ line React codebase to own the TanStack Start and SSR architecture, streaming, and caching strategies.
- Consolidate client state management and harden UI/state separation to ensure a thin, predictable wrapper over backend APIs.
- Build agent-native infrastructure, ensuring all UI actions are accessible to AI agents through decorators and semantic code paths.
Who this is a fit for
- Deep React expertise with production SSR experience and a proven ability to architect large-scale, high-performance web applications.
- AI-native workflow where agents are your primary tool for refactors and building automated verification systems and E2E tests.
- Strong product taste with an interest in music creation and the ability to work in-office 5 days a week in London.
Why this role is remarkable
- Work directly with the founders to own the end-to-end architecture, state, and delivery for a revolutionary social music product.
- Backed by $7M+ from elite investors including Balderton Capital (backers of Revolut) and Kevin Hartz (founder of Eventbrite).
- Tackle extreme engineering challenges like a WASM audio engine, 60fps WebGL rendering, and real-time multiplayer collaboration.
How Jack & Jill work together
I get to know what you’re great at, then find roles you’d never find yourself.Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
I recruit from Jack’s network and make the intro when I spot a great match.And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.
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What happens next?
Jack’s an AI agent for job searching and career coaching. He works for you.
Jill is the AI recruiter working for the company. She recruits from Jack’s network.
If your profile’s a match and Mozart AI wants to meet, Jill will make the intro. In the meantime, Jack will send you excellent alternatives.