Senior Principal Engineer; iOS

Position: Senior Principal Engineer (iOS)
About us At Trainline, our purpose is to empower greener travel choices, connecting people and places. Trainline enables millions of travellers to find and book the best value tickets across carriers, fares, and journey options through our highly rated mobile app, website, and B2B partner channels. Great journeys start with Trainline We’re Europe’s leading independent rail platform, helping millions of travellers find and book the best-value rail and coach journeys across our app, website and partner channels.

Our job is to make the green travel choice the best choice. By building a better train travel experience, we help more people choose rail - creating a positive impact for customers, our business and the planet.

We’re a team of more than 1,000 Train liners from over 50 nationalities, working across London, Paris, Barcelona, Milan, Edinburgh and Madrid. Now is a brilliant time to join us and help shape the future of travel.

Introducing the Trainline App Platform Team The App Platform team provides the foundations that enable our mobile engineering teams to build, evolve and deliver exceptional customer experiences king across iOS and Android, the team develops the shared capabilities, tooling, frameworks and engineering practices that help product teams move faster while maintaining high standards of quality, performance and reliability.

As our Senior Principal Engineer (iOS), you will play a pivotal role in shaping the future of iOS engineering le embedded within the App Platform team, your influence will extend across the wider technology organisation as you define the long-term technical strategy for iOS alongside peers across Android, Web and Architecture. You'll establish a cohesive cross-platform architectural vision, balancing platform-specific innovation with opportunities to simplify solutions, increase consistency and avoid unnecessary duplication.

This is a highly influential individual contributor role where you'll create leverage through technical leadership, partnering with engineers, architects, product, design and senior leaders to solve complex challenges, shape engineering strategy and raise the technical bar across the  this role as the Senior Principal Engineer (iOS), you will...Define and own the long-term technical strategy for iOS, ensuring it supports Trainline's business goals while aligning with the wider architectural vision across mobile, web and platform engineering.

Own and evolve engineering standards, reusable patterns and best practices for iOS across Trainline, creating greater consistency, improving developer experience and enabling teams to build high-quality software more effectively.

Lead organisation-wide technical modernisation programmes that simplify our engineering landscape, improve maintainability and scalability, and enable product teams to deliver faster with confidence.

Partner closely with Principal Engineers, Architects and senior engineering leaders to establish a cohesive cross-platform strategy, identifying opportunities to share capabilities and architectural approaches while making pragmatic decisions about where platforms should remain distinct.

Champion technical excellence through modular, testable and maintainable software design, helping engineering teams adopt practices that improve quality, reliability, performance and long-term sustainability.

Evaluate emerging technologies and AI-enabled engineering practices, identifying where they create meaningful value for developers and customers while balancing innovation with security, operational cost and long-term sustainability.

Influence technical direction across the engineering organisation through clear communication, compelling technical proposals and trusted relationships with engineers, architects, product, design and executive stakeholders.

Mentor and develop senior engineers and members of the Principal Engineering community, while representing Trainline within the wider engineering community through knowledge sharing, technical leadership and community engagement.

We'd love to hear from you if you have...Significant experience defining technical strategy for large-scale iOS…