Senior Mobile Engineer

B2B SaaS | UK Role Overview  Accessible rail travel depends on systems that work reliably in live environments.    Our Passenger Assistance platform turns passenger assistance requests into coordinated action inside live rail operations.    We're hiring a Senior Mobile Engineer to architect, own and ship a greenfield React Native product for iOS and Android alongside our Ruby on Rails engineers.      Strategic Context  Transreport exists to remove structural barriers in rail travel. Our vision is that everyone has access to travel everywhere.    We operate across the UK, Japan, and the EU and have supported over 10 million assistance requests for more than 1.8 million users. We are a Series A company recognised with a King's Award.    As we scale internationally, this role will lead a new React Native application and establish a scalable development environment across iOS, Android, and our backend platform.      Outcomes & Impact  Within 6 months, you will: 

• Architect and launch the first production version of our new B2B React Native application. 
• Establish the greenfield architecture, testing, CI/CD, and release foundations for iOS and Android. 
• Agree scalable API contracts and an integration strategy with our Ruby on Rails engineers. 
• Build trust across Product, Design, and Engineering by surfacing timelines, risks, trade-offs, and technical debt early.    Within 12 months, you will: 
• Own the mobile roadmap across multiple product verticals, from technical design to production. 
• Build a maintainable cross-platform foundation for fast, sustainable delivery. 
• Introduce measurable improvements in mobile quality, stability, performance, and delivery velocity. 
• Shape long-term mobile/backend integration and keep technical debt visible and manageable.        Responsibilities 
•  Architect & Build - Define, own, and ship a greenfield React Native B2B application for iOS and Android. Set architectural standards that balance near-term delivery with long-term scalability. 
• Own Delivery - Own multiple workstreams in a small team, turning product goals into technical plans and carrying them through build, release, and iteration. 
• Design for the Long Term - Make pragmatic greenfield architecture decisions, balancing delivery speed with maintainability, scalability, accessibility, and technical debt. 
• Partner with Backend - Work with Ruby on Rails engineers to shape API contracts, data flows, authentication, observability, and a sustainable mobile/backend boundary. 
• Technical Leadership - Proactively communicate timelines, delivery confidence, dependencies, risks, and trade-offs, helping Product and Engineering make informed scope decisions.    This high-autonomy role suits an engineer comfortable defining what to build, designing the system, and delivering it—not simply implementing prescribed solutions.    The Tech Environment:   Target Stack 
• React Native (TypeScript) 
• React Navigation  Backend & Delivery Context 
• Ruby on Rails APIs 
• iOS and Android app delivery 
• API contracts and mobile/backend integration 
• Automated testing and CI/CD 
• Mobile monitoring and performance optimisation 
• App Store and Google Play release practices 
• Security, accessibility, and maintainable engineering standards    You are not expected to know every tool immediately, but you must be comfortable owning architectural decisions across React Native and its backend integration.    Requirements  Must Haves 
• 6+ years of mobile engineering experience. 
• Deep React Native and TypeScript expertise across architecture, testing, performance, and production delivery. 
• Strong judgement about when React Native needs native platform capabilities or modules. 
• Proven experience designing a greenfield system and shipping production iOS and Android applications. 
• Experience establishing a development environment and technical direction from scratch. 
• Comfortable explaining trade-offs between delivery speed, product needs, and maintainability. 
• Ability to manage ambiguity, own multiple verticals, and move between architecture and hands-on delivery. 
• Strong communication skills, proactively surfacing delivery confidence, risks, dependencies, and technical debt.  Nice to Haves: 
• Experience collaborating with Ruby on Rails or similar backend teams. 
• Experience in transport, logistics, or regulated industries. 
• Familiarity with mobile observability, performance profiling, testing, and app-store releases. 
• Experience working in B2B SaaS environments. 
• Exposure to native iOS and Android development.    Benefits 
• Private healthcare after your probation (including children) 
• Hybrid working model 
• 25 days holiday 
• Volunteering Leave 
• Free flu jab for you and your family      Culture & Operating Principles  We value: 
• Ownership over hierarchy 
• Clarity over bureaucracy 
• Impact over job titles    We operate with high autonomy and high accountability. People are expected to raise risks early, communicate clearly, and take responsibility for outcomes.      Interview Roadmap  Screening Call (30 mins)  Technical Architecture Discussion – Greenfield React Native and backend integration deep dive  Final Culture Conversation – Leadership alignment        Guaranteed Interview Scheme    We also offer a Guaranteed Interview Scheme (GIS) for candidates who consider themselves to have a disability as defined under the Equality Act 2010.    If you indicate this option in your application and your application demonstrates that you meet the essential criteria for the role, you'll be invited to interview or assessment.    Choosing GIS doesn't guarantee a job offer. If you have any questions, please get in touch.