Senior Product Engineer

London · Hybrid, 2 days in office · £65,000–£80,000 + equity + benefits · Permanent We are partnering with an ambitious seed-stage AI startup based in London to hire their first dedicated growth engineer. The company They're building the senior AI employee for small-business owners. It plugs into the tools they already use, watches what they commit to, and drafts the work they owe — client updates, proposals, reports — from their real numbers, ready to approve. No prompting, no setup. Small, senior engineering team. Shipping fast. Everything still to be built. The role You own the loop between what gets shipped and whether it's working. You instrument the funnel, run the experiments, and come back with a clean verdict — not a dashboard for someone else to read. 70% building, 30% analysis. No PM handing you a spec. What you'll own * The activation funnel, end-to-end—instrumentation, finding where users lose momentum, shipping the fixes. * The experiment framework. Clean A/B tests behind feature flags (GrowthBook, PostHog, LaunchDarkly, Statsig) without a two-sprint setup cost — plus the statistical read: significance, sizing, guardrails. * Retention and re-engagement. Nudges, notifications and lifecycle flows in Customer.io, Braze, Iterable or your own. * Tracking the team can trust. A clean Amplitude event taxonomy tied to every ticket, and you query the data yourself in SQL. A gap in the data is yours to fix, not someone else's to flag. * Fast surface features. CTAs, banners, empty states, connector onboarding — shipped in TypeScript and React in days, measured immediately. What we're looking for * You think like a founder: you care about the business number, not the feature, and find the highest-impact bet yourself. * You've shipped growth features at a B2B or pro-sumer company and can point to what moved. * You build with agentic coding tools daily — Claude Code, Cursor or similar. * You've built viral or expansion loops — invite, seat or content-sharing. One user bringing their team is the core loop here. * You're a senior IC who works without direction, writes clean code, and knows when a fix belongs in an experiment and when it doesn't. * You want to talk to real customers, find where they dropped off, and build the fix yourself. *Nice to have: design taste for the surfaces you ship · chat-native products (Slack, Teams) · OAuth connectors · LLM and agent products, prompt engineering, evals · Datadog.* The details * Full-time, permanent, flexible hours. Two days a week together in the London office. * You'll need the right to work in the UK. * Four stages: intro call → technical and product conversation → practical working session → founder conversation. How to apply Send your CV and LinkedIn to us, plus anything that shows how you think and build — GitHub, portfolio, products you've shipped, or a short note. Excited by the role but don't match every line? Get in touch anyway. Pay: £70,000.00-£85,000.00 per year Benefits: * Company pension * Employee stock purchase plan * Free fitness classes * Sick pay Work Location: Hybrid remote in West London