Senior/Staff Product Engineer (Mobile)
Joinfleek.com – Post-Series B marketplace backed by a16z and YC.
Location: London, UK.
Job Description
As a Senior/Staff Product Engineer, you will own the mobile experience for the world's fastest-growing wholesale secondhand fashion marketplace. Joining the London-based Demand team, you will build the primary interface used by 90% of buyers, integrating AI-driven classification into a seamless, high-performance React Native application that directly drives global GMV.
Why this role is remarkable
* Direct ownership of the #1 revenue channel for a hyper‑growth startup tripling year‑on‑year with backing from top‑tier VCs like a16z and Y Combinator.
* High‑impact architectural influence where you define the mobile standards and experimentation layers for a marketplace disrupting a fragmented supply chain across 70+ countries.
* Work in an AI‑first engineering culture under leadership from Google and Postmates, utilizing cutting‑edge tools to solve complex inventory and discovery challenges.
What you will do
* Lead the development of the core React Native application, focusing on high‑polish discovery, browsing, and purchasing flows that convert intent into transactions.
* Partner with data and AI teams to implement mobile surfaces for the FleekSort classification engine, making complex AI grading feel intuitive for users.
* Build and maintain a robust experimentation framework for A/B testing and analytics to drive data‑informed product decisions and optimize conversion rates.
The ideal candidate
* 4‑10+ years of professional software engineering experience with deep, production‑level expertise in React Native and mobile performance optimisation.
* Proven track record in a fast‑paced consumer marketplace or e‑commerce environment where interaction quality and animation polish are treated as core features.
* Product‑mindful engineer who leverages AI tools like Cursor or Copilot and connects technical trade‑offs to commercial outcomes rather than just following tickets.
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