Staff Product Engineer in London

Can you help us fix the world's most broken supply chain? The fashion industry produces over 100 billion garments a year. 60% end up in landfill, not because people don't want these clothes, but because the supply chain for getting secondhand fashion from donation to resale is completely offline, manual, and broken. Fleek is fixing this. Our mission is to make secondhand the first choice. We're building the infrastructure powering the global secondhand clothing trade, through a B2B marketplace and the AI systems digitising the supply chain behind it.

Through Fleek, vintage stores, online resellers, and retail buyers source graded secondhand inventory directly from wholesalers and rag houses across multiple countries. Our key enabler is FleekSort, an AI model fine-tuned on secondhand fashion, that can grade, price, and categorise items with just a photo, turning what has historically been an opaque and manual trade into a structured, searchable, and tradable global inventory layer. Since 2022, we've saved 9 million items from landfill while tripling in size year-on-year. We're backed by some of the world's best investors, including a16z, Y Combinator, and HV Capital, alongside world-class angels who helped build Depop, Shopify, and Postmates. Today, we serve thousands of resellers and retailers across the UK, Europe, and the US. With the secondhand fashion market projected to reach $350B by 2027, Fleek is building the AI-native operational and financial backbone for secondhand commerce globally.

We're looking for people who want to build something that matters, and move fast doing it. Sound good? Keep reading.

About the Role

This is the most senior engineering role in the company. You will own Demand end-to-end, the product surface that drives revenue, growth, and customer love, across mobile, web, and backend. You'll lead a team of ~5 engineers in London, report into our CTO, Sanket Agarwal (ex-Google, Postmates), and partner deeply with Product and Design. If it impacts buyer conversion, retention, or growth velocity, you own it.

Why This Role Stands Out

Demand is the most commercially important function at Fleek. You won't be a Staff engineer who advises from the sidelines, you'll own the entire system that converts supply into revenue. Fleek is digitising an industry that has never had technology. There are no existing playbooks for building a transaction layer around secondhand fashion at wholesale scale, where every item is unique, inventory is unpredictable, quality is graded by AI, and the supply chain spans three continents. You will be designing how this market works.

Your systems will handle 500,000+ items a month today and millions by the end of the year. You'll work closely with our data and AI teams to build the services that connect FleekSort's classification engine to the marketplace experience. You'll set the technical standard for the entire engineering org.

For the first six months, you'll be deeply hands-on, writing production code, owning critical threads, and building context. As foundations stabilise, your impact shifts to direction-setting, multiplying team output, and building an engineering system that scales technically and organisationally. The goal is not to stop coding. The goal is to build an organisation that doesn't depend on you coding.

What Makes You a Fleek Staff Engineer?

• System-Level Thinker: You see the full picture, from the UI a buyer touches, through the API, the data layer, and the infrastructure underneath. You make architectural decisions that compound speed, not just solve today's problem.
• Product-Obsessed Leader: You think about why a buyer drops off at checkout, not just how the checkout service is architected. You instinctively connect technical decisions to commercial outcomes.
• Builder Who Leads: You set direction by shipping, not by presenting. You write code, review code, and raise the bar through demonstration, not delegation.
• Comfortable with Ambiguity: We're building systems for workflows that didn't exist before Fleek. You thrive when the problem is undefined, the scope is broad, and you need to define the path yourself.
• Talent Multiplier: You turn good engineers into great ones. You set standards, create leverage, and build a team that ships without heroics.
• Startup Pace: You've worked in environments where shipping matters more than perfection, where you deploy daily, and where velocity is a competitive advantage.

What You'll Do

• Own the Demand System End-to-End: Design and build the full stack behind the Demand funnel, mobile app, web platform, core backend services, APIs, search, discovery, purchase flows, experimentation foundations, and analytics. These are the product features that directly drive GMV.
• Lead a High-Performance Team: Lead and develop ~5 engineers. Set technical direction, execution cadence, and engineering standards. Raise talent density through hiring and mentorship. Your job is to turn a good team into an elite one.
• Integrate AI into the Product: Build the services that connect FleekSort's AI classification engine to the marketplace experience, ensuring grading, pricing, and categorisation flow seamlessly into listings, search, and buyer workflows.
• Create Engineering Leverage: Remove structural bottlenecks across the Demand stack. Define clean ownership boundaries and platform primitives. Establish observability, release discipline, and performance guardrails. Build systems that compound iteration speed.
• Shape Technical Direction: Set architectural decisions across the Demand stack and influence engineering standards company-wide. Challenge assumptions, propose alternatives, and define how Fleek builds software.
• Collaborate Cross-Functionally: Partner deeply with Product and Design to define what gets built. Work with data, AI, and operations teams to turn complex real-world logistics into reliable, scalable software.

What You Bring

• 10+ years of professional software engineering experience. You've built and shipped production systems that handle real traffic and real money at scale.
• Prior Senior or Staff-level ownership of critical product systems. You've been the person responsible for a system that directly drove revenue or growth, not just a contributor.
• Full-stack in the real sense, UI to API to data to infrastructure. You can make informed decisions at every layer of the stack and understand how they affect each other.
• Strong fundamentals in system design, data modelling, and API architecture. You can design a service from scratch, reason about its failure modes, and explain the trade-offs to a product manager.
• Consumer or marketplace background. You've worked at a marketplace, ecommerce, or consumer product company. You understand what it means to build for end users at scale.
• Experience leading and developing engineers. You've managed or technically led a team. You know how to set standards, give feedback, and create an environment where people do their best work.
• Product engineering mindset. You can articulate the business problem your code solves. You've worked closely with product and design, and you've made trade-offs that balanced user experience with technical constraints.
• Startup or scale-up experience. You've worked in environments with fast deployment cycles, evolving requirements, and high ownership. You ship, learn, and iterate.
• AI first 10x-er. You think about your role as a 10x-er through the lens of AI. You've built AI capabilities either in your spare time or in deployment at scale.

Nice to Have

• Experience with Node.js and TypeScript (our primary backend stack)
• Familiarity with React Native and mobile development
• Experience building experimentation and analytics foundations

Ready to own the most commercially important function at a company tripling annually? If you want to set the technical standard for the organisation, lead a world-class team, and build the system that compounds growth, we'd love to hear from you.

How We Work

Fleek is an in-office company. We believe the best work happens when people are together: the quick decisions, the cross-functional energy, the ability to solve problems in real time. Most of the team works from our London HQ 3–4 days a week. We're not prescriptive about it. Performance and trust matter more than attendance. We hire adults and treat them accordingly.

The Practicalities

• Location: London HQ, Commercial St, E1 (Liverpool St / Aldgate East)
• Work model: In-office, typically 3–4 days per week
• Level: Staff (L6)
• Stage: Post-Series B, hyper-growth
• Team: 100+ across London, India, and Pakistan (~20 in London office)
• Stack: Node.js, TypeScript, React Native, AI/ML integration
• Culture: High ownership, non-hierarchical, fast-moving. Founder-led with strong opinions loosely held.

Our Values

• Dream Big and Disrupt Yourself: Push the most ambitious version of what you're building. Step out of your comfort zone. Nothing is out of reach.
• Absolute Ownership: The buck stops with you. Drive initiatives to completion. Experiment, learn, persevere. The job isn't done until the job is done.
• Curiosity Leads the Way: Don't accept anything at face value. Ask questions you don't know the answer to. That's how you innovate.
• Talk to the Customer: Deeply understand their challenges, motivations, and ambitions. Every decision starts with the customer at the centre.
• Embrace Diversity: A global team building for a global supply chain. Bring your authentic self and embrace the diversity of everyone you encounter.

We're hosting our first-ever hackathon in partnership with Andreessen Horowitz! On Saturday, 11th July, we're opening the Fleek HQ doors in London for a one-day sprint to build the AI that makes circular fashion operate at scale.