Senior AI Engineer (Backend)

📍 London (Hybrid — 2 days onsite) 🕒 Permanent | Start ASAP 💼 Experience: Senior Create the future of travel with us Whether it's to visit the people closest to us, starting an exciting adventure, or a career-defining business trip, travel is an essential part of our lives. Yet we've all experienced the aches and pains of getting to our destination. Today, more than 4 billion airline passengers rely on technology that hasn't kept up with the expectations of the modern connected traveller. That's why we've started to rebuild the infrastructure that underpins the travel industry. We're on a mission to unravel travel — simplifying systems and building the tools that will make the future of travel effortless. We were part of Y Combinator S18's cohort and we are 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 team in London is growing and we're looking for talented people to join us on our journey. AI at Duffel Travel is one of the most demanding domains for AI. A single trip can span multiple airlines, hotels, payments, policies, and time zones — and when something goes wrong, travellers need answers fast. We're building a chat-based AI assistant that helps travellers manage trips booked through Duffel: changing a flight, understanding a fare rule, recovering from a disruption, getting a receipt — all the things that today mean a phone call or a long wait. Behind that experience sits a platform: the orchestration, retrieval, memory, and evaluation systems that let agents reason reliably over real bookings, real money, and real policies. As a senior AI Engineer, you'll help build that platform from the ground up and set the technical direction for how we build agents at Duffel. What you'll get to do Design, ship, and own production-grade AI agents end-to-end — from intent through to taking action against Duffel's APIs — and define the agent development lifecycle the rest of the team will follow. Build the core platform that powers our agents: the orchestration engine, runtime, and primitives that define how agents reason, take actions, and interact with users — keeping them steerable and verifiable while staying conversational and adaptive. Make agents trustworthy. Build the retrieval and grounding systems that ensure responses are accurate, and the evaluation frameworks that let us measure and improve agent quality deliberately rather than vibes-first. Lay the foundations for memory and personalisation: long-term agent memory, reusable customer data primitives, and the optimisation loops that let agents personalise interactions and demonstrably lift business outcomes. What we're looking for in you Significant experience shipping AI agents and LLM systems into production, with strong opinions on the modern toolkit — eval frameworks, agent orchestration, RAG pipelines, prompt engineering — and the tradeoffs between them. A track record of taking ambiguous problems from zero to one, raising the bar for the engineers around you, and shaping technical direction across teams. A strong general engineering foundation. We care more about your ability to design good systems than about any specific language or framework — you'll work across our stack as needed (Elixir on the backend, TypeScript on the frontend). Big picture thinking — you can make tradeoffs on technical work streams against business impact, and know when to ship something rough to learn from versus when to invest. Fantastic communication skills. You're able to articulate what you're working on and why to the team in a clear and structured way. You thrive in a collaborative environment. You believe in your own methods but keep an open mind, taking suggestions and feedback onboard as well. Bonus if you have experience in travel, flights, hotels or cars. A few key pieces of information before applying 📍 Location: We are based in Shoreditch, London and have a hybrid work-from-home policy and require everyone to come to our office on Tuesdays and Thursdays. 📝 Interview Process: Our interview process consists of three stages: a recruiter screen, a hiring manager interview, and a final stage interview. ✔️ Background Checks: If you are successful, all offers will be pending satisfactory background checks (we partner with a third-party provider to do so) and employment references. Why Join Duffel? We’re a growth-focused team that values open communication, diverse perspectives, and true ownership. We want you to feel empowered in your role, which is why every permanent employee becomes a company shareholder. 🌍 Live Your Best Life Duffel Travel Allowance: We subsidise your wanderlust. Work From Anywhere (60 days): Your office, your rules. Sabbaticals: Long-term loyalty, long-term breaks. Flexible Bank Holidays: Swap holidays to suit your schedule. 🔋 Level Up & Give Back Study Days: Get paid to learn. Volunteering Day: One day a year to save the world. Electric Car & Cycle Schemes: Eco-friendly rides, tax-free prices. 🛡️ The Essentials, Upgraded Family Leave (maternity, paternity and adoption): Big support for life’s biggest moments, 26 weeks fully paid. Pensions & Loans: Future-proofing and interest-free commuting. Eye Tests: Keeping your vision (and your style) sharp. We are an equal opportunities employer. We believe that the key to our success is employing a diverse team, that's why recruitment decisions are only based on your experience and skills. We value your ability to problem solve and build amazing things so we welcome applications for everyone - regardless of age, sex, disability, sexual orientation, race, religion or belief. Note to recruitment agencies Duffel does not accept speculative CV's from external parties. Any unsolicited CV's sent to us will be treated as property of Duffel, and any attached terms and conditions associated with these CV's will be null and void.