Product Engineer - Full-Stack Developer

About Liftoff

Our Mission: Making the world a better, healthier place by gamifying fitness Liftoff is the Duolingo of fitness, empowering anyone to start and stay at the gym so they develop healthier, more powerful habits. We’re a mission-driven team that moves fast, owns the details, and does the work. We’re fully bootstrapped, profitable, and built from zero to $8M+ ARR in under two years.

About the Team

You’ll join the Product team and work closely with the Head of Product, collaborating with Engineering, Design, and Growth. Our product is the engine behind everything: retention, monetization, and ultimately revenue. This role is for someone who wants end-to-end ownership over backend reliability and experiment velocity, and loves shipping.

About the Role

We’re hiring a Full-Stack Engineer to ship product features and experiments end-to-end. Your core focus areas:

• Feature delivery across the stack in TypeScript, from React Native screens to Supabase data
• Polished, correct UI, shipped to the standard of the design, not an approximation of it
• Experiment infrastructure and instrumentation
• Clean, performant API and data access
• Cross-functional shipping with Product, Design, and Growth

This is a high-ownership role. You’ll take a problem from spec to shipped, work with our existing team/resources, and own the outcome, not just your slice of it.

What Success Looks Like

• Features and experiments that go out end-to-end without stalling on handoffs
• UI that ships pixel-correct and feels right; spacing, states, edge cases, and transitions handled without needing a review pass to catch them
• A high-velocity experiment pipeline: clean instrumentation → fast implementation → reliable measurement → iteration
• A product that stays fast and stable as usage grows; schema changes land safely, queries stay efficient
• Shipped improvements that compound (reusable experiment patterns, better event tracking, faster deploys, fewer incidents)
• Strong operating cadence with crisp communication on what's shipping, why, and what it did

What You’ll Do

• Ship features end-to-end
• Build the front end in TypeScript with React Native (Expo); typed, readable, and maintainable by the next person
• Implement designs faithfully: correct spacing and type, all states (loading, empty, error), and the edge cases the mock doesn't show
• Write and run migrations and deploy schema changes safely; keep the data model clean as the product grows
• Stay conscious of load and performance - catch the slow query or the runaway request pattern before users do
• Ship experiments and instrumentation
• Partner with Product/Growth to implement A/B tests and feature flags via Statsig
• Ensure every experiment has clean event tracking and reliable data
• Build reusable patterns that reduce experiment cycle time
• Use data to drive decisions
• Instrument events properly so the team can trust experiment results
• Spot measurement issues (leaky cohorts, misconfigured flags, underpowered tests) before they corrupt decisions
• Collaborate cross-functionally
• Work with Product and Growth to align experiment implementation with the roadmap
• Work with Design to turn Figma into shipped UI in React Native / Expo
• Contribute to prioritization by bringing technical feasibility and effort estimates

You’ll Likely Succeed If You Have

We don’t expect you to check every box. We care most about ownership, judgment, and shipping.

• Professional full-stack experience shipping to production
• Strong TypeScript — it's the language of the whole stack here, front end included
• Comfort on both sides: modern front-end (React / React Native or similar) and Node.js against a relational database (Postgres preferred)
• A real eye for detail; noticing unwanted 4px gaps, missing empty states, animation stutters, and fixing it without being asked
• Working knowledge of schema design, migrations, and query performance, enough to make changes safely without needing a specialist
• Hands-on experience with experimentation infrastructure: feature flags, A/B tests, event tracking
• Demonstrated ability to ship autonomously in a fast-paced, low-structure environment
• Clear written communication; can document decisions, write specs, and share learnings

Bonus Attributes

UX instinct — you can tell when a flow doesn't feel right, not just when it doesn't match the spec, and you can articulate why and push back on a design

• Experience with our specific stack: Supabase, Vercel, tRPC, Statsig, RevenueCat
• Background in subscription/consumer apps — understanding of trials, paywalls, LTV, ARPU
• Experience with AI-assisted development workflows
• Prior experience at a fast-moving startup where you wore multiple hats
• Motion/animation implementation (Rive or similar)

Tools & Tech Stack

• Language: TypeScript, end to end
• App: React Native (Expo)
• Frontend: Figma, Rive
• Backend: Supabase, Vercel, tRPC, Node.js
• Monetization: RevenueCat, Superwall
• Experimentation / Analytics: Statsig

At Liftoff, You’ll Enjoy

• Autonomy and Ownership: you are in charge of your time at Liftoff. Decide what you want to do, align with leadership, and go for it.
• Top-of-the-Market Cash & Equity Compensation: we pay for high performers.
• A World-Class Team: low-ego, high standards, and real ownership.

Interview Process

• Hiring Manager Screening
• Take-Home Challenge (backend task + frontend implementation) Technical Deep Dive (live walkthrough + system design extension)
• Work week trial (paid - simulating real work environment)

Compensation and Benefits

• Competitive cash (based on level and scope)
• Company-paid lunch every day (if you’re in office)
• Lifetime Liftoff Pro membership

Equal Opportunity Liftoff is an equal opportunity employer. We hire and grow talent based on strengths, potential, and performance, and we are committed to building an inclusive environment where everyone can do their best work.