Senior Backend Software Engineer
You will work with Node.js, TypeScript, and the proprietary FleekSort AI classification engine, using AI tools like Cursor or Copilot. You will own the core ecommerce journey for the Growth squad, building backend systems for discovery, payments, and seller tools for a secondhand fashion marketplace.
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Job Title
Senior Backend Software Engineer
Salary
£100k–£140k + Equity
Company Description
Fleek is a ~$50M Series B startup backed by a16z and Y Combinator, building the AI-native infrastructure for the $350B global secondhand fashion market.
Job Description
You will join the Growth squad to own the core ecommerce journey, building backend systems for discovery, payments, and seller tools. Reporting to the CTO, you'll integrate the proprietary FleekSort AI classification engine into a marketplace handling millions of items. This role is about digitizing a broken, manual supply chain at global scale.
Location
London, UK
Why this role is remarkable
Work on a genuinely novel technical challenge by integrating FleekSort, a custom AI model (not a GPT wrapper) that digitizes opaque secondhand inventory.
Join a hyper-growth company tripling year-on-year with ~$50M in funding from top-tier investors like a16z, Y Combinator, and HV Capital.
Deliver massive environmental impact by building systems that have already saved 9 million items from landfills and are scaling to serve thousands of global retailers.
What You Will Do
Architect and own the end-to-end ecommerce journey, including item discovery, search, multi-currency payment systems, and credit infrastructure.
Design and scale backend services to handle over 1 million unique items per month, connecting AI grading engines to real-time marketplace workflows.
Collaborate in a senior product squad to translate complex international logistics and supply chain challenges into reliable, high-performance software.
The ideal candidate
Has 6-10 years of professional backend experience, ideally using Node.js and TypeScript, with a proven track record of shipping high-traffic production systems.
Possesses a product engineering mindset from a consumer-facing marketplace or fintech background, focusing on commercial outcomes rather than just infrastructure.
Thrives in early-stage, fast-paced environments (Seed to Series B) and utilizes AI tools like Cursor or Copilot as a force multiplier in their workflow.