Senior Engineer

Senior Software Engineer London | Full-time | Hybrid | Shoreditch/Liverpool Street Create the Future of Travel With Us Whether it's visiting the people closest to us, starting an exciting adventure, or a career-defining business trip, travel is essential. Yet we've all experienced the aches and pains of getting to our destination. More than 4 billion airline passengers rely on technology that hasn't kept up with modern expectations. That's why we're rebuilding the infrastructure that underpins the travel industry - simplifying systems and building tools that will make the future of travel effortless. We were part of Y Combinator S18's cohort and we're backed by Benchmark, Blossom, Index Ventures, and Kima Ventures - a fantastic set of investors that has helped build some of the world's largest companies. Our London team is growing, and we're looking for a Senior Engineer to help shape both the product and the team building it. Engineering at Duffel We're building tools to simplify travel distribution, search, and booking through one seamless API. The technical challenge? Design a world class API, then integrate it with a vast number of travel providers - each with different systems and requirements - whilst delivering a fantastic developer experience. We work with Elixir, Phoenix, Kubernetes, and Google Cloud Platform, but we value strong engineering fundamentals over specific tech experience. As a Senior Engineer, you won't just execute against a spec - you'll help define what gets built and how. You'll take on ambiguous problems, shape technical decisions across teams, and set a bar for quality that others follow. You'll Thrive Here If: ✅ You've designed and shipped APIs at scale, and have a clear point of view on what makes a great one ✅ You can take a loosely-defined problem and turn it into a clear technical plan, working independently - weighing technical rigour against business impact along the way ✅ You think in systems: you can trace how a decision in one part of the stack ripples into others, and design with those knock-on effects in mind ✅ You want to keep writing production code as a senior engineer, not move away from it - this role is hands-on for the long run, not just at the start ✅ You've mentored engineers or helped them do their best work, and take real satisfaction in others reaching the bar you hold yourself to ✅ You communicate clearly, articulating what you're working on, why, and the reasoning behind your tradeoffs, in a structured way, to a variety of internal and external stakeholders. ✅ You thrive collaboratively - you believe in your methods but stay open to feedback and suggestions, and know when to stand by your approach and when to compromise Bonus: Experience in travel, flights, hotels, or cars What You'll Get: 💰 Competitive salary + equity (you'll own part of Duffel) 🏝️ Work from anywhere policy 🏥 Private Healthcare 🛩️ Duffel travel allowance (use what we build) 🍼 Matched Family leave 🧘‍♂️ Sabbatical programme (3 months full pay) 🪩 Office in Shoreditch + regular team socials Why Now Matters You'll work on the core API powering millions of travel bookings, with real influence over its direction. Early-stage role = outsized impact on how we build and scale, and a seat at the table for the technical decisions that will define the next phase.