Senior Backend Software Engineer (£100k–£140k + Equity) at $50M Series B AI-native marketplace

Job Title

Senior Backend Software Engineer

Salary

£100k–£140k + Equity

Company Description

$50M Series B AI-native marketplace backed by a16z and Y Combinator

Job Description

You will join the Growth squad to build the transaction layer for the world’s first digital supply chain for secondhand fashion. Reporting to the CTO (ex-Google, Postmates), you will integrate fine‑tuned AI models into a B2B marketplace handling 500,000+ items monthly, turning manual trades into a structured, searchable global inventory layer.

Location

London, UK

Why this role is remarkable

• Work at the intersection of circular economy and proprietary AI, using a fine‑tuned model (not a GPT wrapper) to digitize a $350B industry that has never had technology.
• Massive financial backing with ~$50M raised from elite investors including a16z, Y Combinator, and HV Capital, plus advisors from Depop and Shopify.
• High‑velocity environment where you will see immediate impact, helping save millions of garments from landfills while the company triples in size year‑on‑year.

What You Will Do

• Architect and scale backend systems in Node.js and TypeScript to handle the transition from 500k to millions of unique items per month.
• Own the end‑to‑end ecommerce journey, including discovery, search, checkout, and complex international payment and credit systems.
• Collaborate with AI and data teams to bridge the gap between classification engines and the core marketplace product experience.

The ideal candidate

• 6–10 years of professional backend experience with strong fundamentals in system design and API architecture at high‑growth consumer or marketplace companies.
• Proven product engineering mindset with a history of shipping end‑to‑end features in fast‑paced, ambiguous startup environments.
• AI‑forward builder who uses tools like Cursor or Copilot as a force multiplier and has experience deploying AI capabilities at scale.

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