You will architect the transaction layer for the world’s first AI-native secondhand fashion marketplace. Reporting to the CTO, you will build scalable systems handling 500k+ items monthly, integrating proprietary computer vision models into core ecommerce flows. This is a high-impact role digitizing a $350B industry while diverting millions of garments from landfills.
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London, UKNot Disclosed
Featured roleLondon, UKNot Disclosed
Senior Backend Software Engineer at Joinfleek.com — AI-powered B2B marketplace
Join Joinfleek.com, a Series B startup backed by a16z and Y Combinator that's fixing the world's most broken supply chain. As a Senior Backend Engineer in London, you'll build the AI-native infrastructure powering a $350B secondhand fashion market. From scaling systems that handle 500,000+ items monthly to integrating proprietary computer vision models into the core marketplace, you'll have a front-row seat to the future of circular commerce. If you're a product-obsessed builder who thrives in high-ownership environments and wants to save millions of garments from landfills, this is the role for you.
Overview
Why this role stands out
Company
Technology100
Joinfleek.com - Series B fashion-tech marketplace backed by a16z and YC
Responsibilities
What you will do
- Design and scale backend systems for item discovery, search, and complex multi-continent payment and credit workflows.
- Architect the integration between FleekSort’s AI classification engine and the live marketplace to enable real-time inventory structuring.
- Lead technical direction within a senior squad, mentoring junior engineers and defining engineering standards for a rapidly growing 100-person team.
Candidate profile
Who this is a fit for
- 3–6 years of backend experience with Node.js and TypeScript, specifically building high-traffic consumer marketplaces or fintech products.
- Proven ability to design complex system architectures and data models from scratch while navigating the ambiguity of a fast-paced startup.
- Product-minded engineer who prioritizes commercial outcomes and user experience over pure technical perfection, ideally with interest in AI deployment.
What makes it remarkable
Why this role is remarkable
- Join a hyper-growth Series B startup that has raised ~$50M from top-tier investors including a16z, Y Combinator, and HV Capital.
- Work on FleekSort, a proprietary AI model that is fundamentally transforming global supply chains by automating the grading and pricing of unique items at scale.
- Massive environmental impact: the platform has already saved 9 million items from landfills and is tripling in size year-on-year.
Jack & Jill
How Jack & Jill work together
I get to know what you’re great at, then find roles you’d never find yourself.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.
I recruit from Jack’s network and make the intro when I spot a great match.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.
About Jack & Jill
Meet Jack
Jack gets to know what you are great at, what you want next, and makes sure Jill considers you for the right opportunities.
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.
Jack