Senior Product Engineer

Senior Software Engineer/Senior Product Engineer | TypeScript, React, Next.js | £90,000–£120,000 + Equity📍 Waterloo, London (3 days per week)💰 £90,000–£120,000 + Equity⚙️ TypeScript, React, Next.js, PostgreSQL, Docker🚀 Freshly Funded AI StartupI'm working with a rapidly growing AI-powered software business on a Senior Software Engineer hire and genuinely think it's one of the more interesting opportunities in London right now.The CompanyThe business is building the operating system for the professional secondhand goods market.The global resale industry is booming, but managing inventory across multiple marketplaces remains surprisingly manual. Professional sellers often list products across eBay, Vinted, Depop and Shopify simultaneously. When an item sells on one platform, it needs removing everywhere else immediately. If it doesn't, you've oversold stock and created a customer problem.Their platform solves this through AI-powered tooling that handles listing creation, pricing, inventory management and marketplace synchronisation automatically.Already operating across the UK, US, Australia and New Zealand, the platform processes 1–2 million items annually and is trusted by organisations including Yorkshire Cancer Research, Crisis and Sense.Following two years of profitable growth, the company has recently raised £1.5m to accelerate expansion.The Engineering ChallengeThe platform works brilliantly on the happy path.The difficult part is everything that happens outside it.What happens when one marketplace goes offline? How do you recover state? How do you maintain consistency across multiple external systems you don't control? How do you ensure inventory remains accurate when thousands of items are being synchronised across different platforms simultaneously?These are the kinds of problems the engineering team spends its time solving.This role sits at the centre of those challenges and will play a major role in shaping how the platform scales over the coming years.The RoleThe engineering team is currently four people and is expected to grow to seven or eight over the next year.One of the existing Senior Engineers is moving into a Tech Lead position, creating an opportunity for someone to join as one of the most influential individual contributors in the business.You'll be:Designing and building systems that synchronise inventory across multiple external marketplaces in real timeSolving distributed systems challenges around consistency, reliability and failure recoveryInfluencing platform architecture as the business scales internationallyWorking across TypeScript, React, Next.js, PostgreSQL and AI-powered workflowsImproving observability, performance and operational resiliencePartnering closely with founders, customers and engineers to shape product directionMentoring junior engineers and helping establish engineering best practices as the team growsThis is not an environment where engineers simply receive tickets. You'll be expected to understand the product, challenge assumptions, identify risks early and contribute to technical and product decisions.What They're Looking ForStrong experience building SaaS products in production environmentsExcellent engineering judgement and pragmatic decision makingExperience with distributed systems and platform scalabilityStrong database knowledge and system design fundamentalsComfortable operating in startup or scale-up environmentsProduct-minded engineers who care about outcomes as much as implementationTechnology is less important than engineering fundamentals. Engineers from TypeScript, Python, Go, Java or C# backgrounds would all be considered.Why Join?£1.5m recently raised following two years of profitable growthEquity package with meaningful upsideEngineering team growing from 4 to 8 peopleOpportunity to influence architecture and technical direction from an early stageComplex distributed systems and platform-scaling challengesWork directly alongside a Cambridge Computer Science founder and a former Red Gate Software CEO, both highly technical leaders with a strong track record of building successful software businessesReal customers across four countries relying on the platform every dayHigh-ownership environment where engineers have genuine influence on product and technical decisionsThe OpportunityThe engineering team is still small enough that every hire changes the trajectory of the business.The platform has product-market fit, paying customers, fresh funding and significant room to grow internationally. For the right engineer, this is an opportunity to join before the scale arrives and help shape what comes next.Senior Software Engineer/Senior Product Engineer | TypeScript, React, Next.js | £90,000–£120,000 + Equity