Senior Principal Engineer iOS

Salary: £65,000 - 105,000 per year

Requirements:

• Significant experience defining technical strategy for large-scale iOS platforms or products, with a track record of delivering architectural improvements that have created lasting impact across multiple teams or organisations.
• Deep expertise in modern iOS development, alongside strong experience designing modular, testable and maintainable software that balances scalability, reliability, performance and long-term maintainability.
• Experience establishing engineering standards, technical patterns and best practices, with the ability to influence their adoption across an organisation through technical credibility and collaboration.
• A proven ability to create alignment across engineering disciplines, working closely with architects, product, design and technology leaders to develop shared technical direction and deliver business outcomes.
• Strong judgement when evaluating emerging technologies, including AI-enabled engineering capabilities, with the ability to identify where they can create genuine value while balancing cost, risk and long-term sustainability.
• Excellent communication and influencing skills, with the ability to adapt your style to engage audiences ranging from hands-on engineers to senior and executive stakeholders.
• An active presence within the wider iOS engineering community through speaking, mentoring, open-source contributions or community engagement is desirable, though not essential.

Responsibilities:

• Define and own the long-term technical strategy for iOS, ensuring it supports our 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 our company, 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 our company within the wider engineering community through knowledge sharing, technical leadership and community engagement.

Technologies:

• AI
• Android
• Mobile
• Security
• Web
• iOS
• Embedded

More:

We are Trainline, champions of rail building a greener, more sustainable future of travel. Our app, website and B2B partner channels help millions of travellers find and book the best value tickets across carriers, fares and journey options. We are Europes number 1 downloaded rail app, with over 135 million monthly visits and 6.3 billion in annual ticket sales, working with 270+ rail and coach companies in over 40 countries. We are a FTSE 250 company with a team of over 1,000 people from 50+ nationalities, based across London, Paris, Barcelona, Milan, Edinburgh and Madrid. The Senior Principal Engineer (iOS) role sits within our App Platform team, which provides the foundations for mobile engineering teams to build, evolve and deliver exceptional customer experiences at scale across iOS and Android. We offer fantastic perks including private healthcare and dental insurance, a generous work from abroad policy, share purchase plans, an EV Scheme, extra festive time off, excellent family-friendly benefits, transparent pay bands, personal learning budgets and regular learning days. We work in a hybrid model and ask our Trainliners to work from the office a minimum of 60% of their time over a 12-week period, with a 28-day Work from Abroad policy. We value Think Big, Own It, Travel Together and Do Good, and we are committed to building an inclusive workplace where everyone belongs.

last updated 34 week of 2026