Senior Mobile Engineer - React Native

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 and tripled in size year-on-year. We've raised ~$50M from a16z, Y Combinator, Burda Principal Investments, HV Capital, and others, and have recently closed our Series B. Our advisors and private investors include operators behind 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.

About the Role: This is a Senior Mobile Engineer role on Fleek's Demand team — the function responsible for growth, conversion, and customer experience. You'll work closely with the Staff Engineer for Demand and partner deeply with Product and Design in London. You’ll own the mobile experience that buyers interact with daily. If it affects how a buyer discovers, evaluates, or purchases inventory on Fleek — it runs through your code.

Why This Role Stands Out: Mobile is the primary surface for Fleek’s buyer experience. You won’t be maintaining an app — you’ll be building the product that converts intent into transactions across a marketplace unlike anything that’s existed before. Every item on Fleek is unique. Inventory is graded by AI, sourced from multiple countries, and moves fast. The mobile experience needs to make this complexity feel effortless — fast browsing, intelligent discovery, seamless purchasing. You’ll work closely with our data and AI teams to bring FleekSort’s classification engine into the buyer’s hands. This isn’t a feature factory. You’ll be shaping product decisions, challenging design trade-offs, and defining the mobile architecture for a marketplace that’s tripling year-on-year. The Demand team in London is small, senior, and moves fast.

What Makes You a Fleek Mobile Engineer?

• Craft-Obsessed Builder: You care about interaction quality, animation polish, and the 50ms that separates a good experience from a great one. You connect UI decisions to conversion outcomes.
• Product-Minded, Not Ticket-Minded: You think about why a buyer drops off mid-scroll, not just what the spec says. You instinctively connect technical decisions to commercial impact.
• Comfortable with Ambiguity: We’re building mobile experiences for workflows that didn’t exist before Fleek. You thrive when the problem is undefined and collaboration is key.
• Owner, Not Renter: You take a feature from problem definition to production and monitor it afterwards. You don’t wait for someone to hand you a Jira ticket.
• Startup Pace: You’ve worked in environments where shipping matters more than perfection, where you release weekly, and where velocity is a competitive advantage.

What You’ll Do:

• Own the Mobile Buyer Experience: Build and scale the React Native app that powers Fleek’s core marketplace — browsing, discovery, purchasing, and post-purchase. These are the flows that directly drive GMV.
• Integrate AI into the Product: Build the mobile surfaces that bring FleekSort’s AI classification engine to buyers — ensuring grading, pricing, and categorisation translate into intuitive, fast, and trustworthy UX.
• Ship with Craft and Velocity: Maintain release stability, reduce crash rates, and improve performance across devices — while shipping new features at startup pace. We optimise for velocity without fragility.
• Shape Product Direction: Work embedded with Product and Design to define what gets built. Challenge assumptions, propose alternatives, and bring technical trade-offs into product conversations early.
• Build the Experimentation Layer: Instrument the mobile app for A/B testing and analytics. Create the surfaces that let the Demand team run experiments and make data-driven product decisions.
• Raise the Bar: Contribute to architectural decisions, improve code quality and long-term maintainability, and help define engineering standards for mobile at Fleek.

What You Bring:

• 4–8+ years of professional software engineering experience. You’ve built and shipped production mobile apps that handle real users and real transactions.
• Strong production experience with React Native. You’re deeply comfortable with the ecosystem and can navigate the boundary between React Native and native platform code.
• UI craft and performance instincts. You have strong opinions on interaction quality, responsiveness, and what makes a mobile experience feel premium.
• Comfort working across mobile and backend boundaries. You can read an API contract, understand the data model behind it, and have informed opinions about how the backend should serve the mobile experience.
• 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.
• 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 mobile experimentation frameworks and feature flagging.
• Familiarity with app store optimisation and release management at scale.

A genuine excitement for building the mobile product that powers the world’s fastest-growing secondhand marketplace. Ready to build the mobile experience for the world’s fastest-growing fashion economy? If you want to work on genuinely hard problems, with a world-class team, at a company that’s tripling annually — 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. For your first six months, we’ll ask you to prioritise being in the office — to learn the business, build relationships, and get up to speed. After that, you’ll have genuine flexibility to manage your own time. We hire adults and treat them accordingly.

The Practicalities: Location: London HQ — Heneage Street, E1 (Shoreditch / Aldgate East). Work model: In-office, typically 3–4 days per week. Full-time in the office for your first six months, then genuine flexibility earned through trust and performance. Level: Senior (L5). Stage: Post-Series B, hyper-growth. Team: 100+ across London, India, and Pakistan (~20 in London office). Stack: React Native, TypeScript, AI/ML integration. Culture: High ownership, non-hierarchical, fast-moving. Founder-led with strong opinions loosely held.

Our Values: Five values shape how we work at Fleek:

• 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.