Founding Mobile Engineer

Mozart AI; Greater London; On-site; GBP 90,000 - 120,000; Full time

Job summary

Mozart AI in London is seeking a senior mobile engineer to own the Mozart app end to end. You’ll lead architecture, RN/Expo app, native Swift and Kotlin where needed, and ship weekly with solid performance and a great UX.

You’ll optimize for background/offline, real-time collaboration, audio playback, and social features, balancing platform differences and backend contracts. 5+ years in mobile development required; in-person role.

Qualifications

• 5+ years of professional mobile development experience.
• Proven ability to own a large production React Native/Expo app.

Responsibilities

• Own the Mozart mobile app architecture, state management, and navigation.
• Make complex product experiences feel simple across music, video, and social features.
• Enable multiplayer, presence, and offline/online sync for mobile sessions.
• Build for background, offline, and energy-efficient performance on phones.
• Ensure high-quality audio playback with responsive controls and platform integrations.
• Ship updates rapidly with measurable release events and robust analytics.

Skills

React Native

Mobile architecture

State management

Performance profiling

Cross-platform mobile

Tools

Swift

Kotlin

Job description

About the Role

Mozart AI is music's first creation network, where the world goes from listening to music, to making it together, to being known for it. 1.5 billion people can play an instrument. We're building the products that turn them into artists, and turn their fans into the next ones. Our customers love us, and include everyone from grandmas using Vibe sessions to Grammy winners using the Studio. Music is having its first explosive moment of creation-driven consumption, and we aspire to shape that world to preserve the social and fun elements of music creation.

We've raised over $7M from Balderton Capital (backers of Revolut) and several Silicon Valley legends like Kevin Hartz and Emery Wells, who have backed companies like Uber, Spotify, Reddit, and other massive consumer outcomes.

We're a small, talent-dense team building the future of music from our London office. We operate with high ownership, high velocity, and low-ego collaboration — specialist generalists who work hard, learn fast, and ship relentlessly. We care deeply, move fast, and we're here to build something that outlives us.

About the Role

You’ll own the Mozart mobile app end to end, React Native and Expo on top, Swift and Kotlin where the platform demands it. Generations, multiplayer sessions, background audio, offline projects, and cloud sync all have to run smoothly on a phone, and you’ll build the foundations that let us ship every week without breaking any of it.

This is an intense, in-person role, built for people who want massive impact and grow their careers faster than anywhere else.

What You'll Do

• Own the app. Architecture, state management, and navigation for our React Native and Expo app, on the same backend contracts the web app uses, with startup, frame rate, memory, and battery measured and tracked.
• Make a complex product feel simple. Music, video, and image generation, editing, collaboration, listening, and a social network in one app. You’ll design the navigation model where everything is one or two taps away and it feels like one coherent product.
• Bring multiplayer to the phone. Presence, shared session state, and conflict resolution that survive backgrounding and network switches.
• Build for background and offline. Own the persistent job system on the phone: generations that finish while the app is closed, uploads and downloads that survive app kills, local songs and projects, and sync that resolves cleanly on reconnect.
• Make audio first-class. Background playback, system controls, interruptions, Bluetooth and AirPlay, and multi-track playback that stays in sync on a phone.
• Build the social layer for touch. Media-heavy feeds at full frame rate, audio previews, publishing, sharing into the platforms people already use, and push notifications for jobs, collaborators, and social activity that deep-link into the right screen with state already loaded.
• Go native where necessary. Swift and Kotlin where the platform demands it, and the newest iOS and Android capabilities before React Native catches up.
• Own the runtime boundary. Real-time audio runs in native code, the app logic runs in Hermes, and you decide how the two talk: what crosses the bridge, what bypasses it, and what never touches the JS thread.
• Own delivery and measurement. Over-the-air updates, binary releases, store review, force-update policy, install attribution, and a typed event layer so every release and campaign is measurable.

What We’re Looking For

• React Native depth. You have built and maintained a large production React Native and Expo app, know the framework's limits, workarounds, and have profiled and fixed frame drops, memory pressure, and slow startup on real devices.
• Native fluency. React Native is your default, but you have written enough Swift and Kotlin to build the whole app natively if it came to that. You follow every OS release and are the first in the room to know what a new API makes possible.
• State management. You have designed store architectures that stay predictable across screens, background events, offline queues, and server pushes.
• Background and offline systems. You have shipped persistent background tasks, downloads, or local-first data on mobile and know what iOS and Android will and will not let an app do.
• Audio on mobile. You have worked with background audio sessions, system playback controls, and interruption handling on at least one platform.
• Obsessed with the experience. You hold the app to the standard of the best consumer apps on the phone, and you can point to work you have shipped that proves it. You notice a dropped frame or a confusing screen before users report it.
• Backend awareness. You know enough about the backend to say when an endpoint is wrong for mobile and to drive the shared contract that fixes it for web and mobile at once.
• Attribution and analytics. You have wired deep links and attribution SDKs and treated analytics as part of the feature, not a follow-up.
• AI-native. You work with coding agents daily and design tests and environments so an agent can verify a change on its own.
• High ownership, low ego. You ship fast, own outcomes after release, and do whatever needs doing
• 5+ years of professional experience

Nice-to-Haves

• Real-time collaboration on mobile (presence, shared state, CRDTs)
• Widgets, Live Activities, App Intents, or other deep OS integrations
• In-app purchases and subscription flows (RevenueCat, StoreKit, Play Billing)
• Routing users between app and web: subscription checkout outside the store, universal and deferred deep links, and clean fallbacks when the app is not installed
• Mic recording or media capture on mobile
• Experience shipping consumer apps at an early-stage startup