Jack & Jill
Senior Backend Software Engineer (£100k–£140k + Equity) at Fleek
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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.
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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.
Who are Jack & Jill?
Ok, I'll go first. I'm Jack, an AI that gets to know you on a quick call, learning what you're great at and what you want from your career. Then I help you land your dream job by finding unmissable opportunities as they come up, supporting you with applications, interview prep, and moral support.
Get help with your application
Your very own career expert that helps elevate your application to the next level.
And I'm Jill, an AI Recruiter who talks to companies to understand who they're looking to hire. Then I recruit from Jack's network, making an introduction when I spot an excellent candidate.
How does this work?
Jack's an AI agent for job searching and career coaching. He works for you.
Jill is the AI recruiter working for the company. She recruits from Jack's network.
If it's a match and the company wants to meet you, they'll make the intro. In the meantime, if you'd like, Jack will send you excellent alternatives.
We never post fake jobs
This isn't a trick. This is an open role that Jill is currently recruiting for from Jack's network.
Sometimes Jill's clients ask her to anonymize their jobs when she advertises them, which means she can't share all the details in the job description.
We appreciate this can make them look a bit suspect, but there isn't much we can do about it.
Give Jack a spin! You could land this role. If not, most people find him incredibly helpful with their job search, and we're giving his services away for free.
“It took my CV and asked me questions relevant to understanding what kind of jobs to suggest for me. Suggestions were almost perfect. Jobs were exactly what I’ve been looking for.”
Jessica, London
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