About the job

Duffel is rebuilding the core infrastructure that powers the global travel industry, modernising how flights and travel services are distributed, searched, and booked through a single, developer-first API relied on by millions of travellers worldwide. As a Senior Software Engineer in London, you will play a key role in designing, building, and scaling backend systems that integrate with hundreds of travel providers, each with unique legacy systems and constraints, while maintaining a reliable, elegant, and high-performance developer experience. You will contribute senior-level engineering judgment to API design, system architecture, and code quality, help define and evolve engineering standards and processes, and make thoughtful trade-offs between technical excellence and business impact. The role values strong software engineering fundamentals over specific language expertise, with the current stack including Elixir, Phoenix, Kubernetes, and Google Cloud Platform. You will collaborate closely with other engineers in a hybrid/on-site environment, communicate clearly about technical decisions, and influence how Duffel’s platform scales as usage grows. Duffel offers a competitive salary and equity package, flexible work-from-anywhere policy, a travel allowance to use the product you help build, matched parental leave, a fully paid three-month sabbatical programme, visa sponsorship, and a Shoreditch office with regular team socials. Backed by Y Combinator (S18), Benchmark, Index Ventures, Blossom, and Kima Ventures, this senior role offers outsized impact on the core API powering millions of travel bookings at a fast-growing travel technology company.