Senior Mobile Engineer (React + Android) in London

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Job Description
B2B SaaS | Hybrid – 2-3 days office | 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 lead greenfield builds and complex migrations across our real-time rail mobile systems.
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 million users. We are a Series A company recognised with a King’s Award.
As we scale internationally, this role will lead the development of a React application to support evolving B2B requirements while modernising our Android platform and strengthening cross-platform alignment.
Outcomes & Impact
Within 6 months, you will:
Architect and launch the first production version of our new B2B React application. Provide reliable senior-level cover for the Kotlin Android codebase. Establish clear migration principles for introducing React into an existing environment. Build trust across Data, Product, and Mobile teams as a technical bridge.
Within 12 months, you will:
Deliver a phased migration roadmap from monolithic Android to React . Reduce platform risk while increasing cross-platform feature parity. Introduce measurable performance improvements in mobile stability and delivery velocity. Influence long-term mobile architecture decisions across the organisation.
Responsibilities
Architect & Build - Design and ship a new React B2B application from scratch using TypeScript, React Navigation, and modern animation libraries. You will define architectural standards and ensure scalability from day one. Maintain & Stabilise - Provide senior-level coverage for the existing Kotlin Android application (Clean Architecture, MVVM). Ensure stability for both staff-facing and passenger-facing applications operating in live rail environments. Strategise Migration - Formulate and execute a safe, phased plan to deconstruct the existing monolithic Android app and rebuild functionality in React without disrupting current operations. Bridge & Cross-Platform - Write modules where necessary and ensure high-performance interop between Kotlin and JavaScript/TypeScript using the React Bridge and JSI. Cross-Team Alignment - Work closely with the Swift/iOS engineer to ensure migration plans align with iOS architecture and roadmap priorities. Collaborate with Data and Product teams to balance commercial speed with platform stability.
This is a high-context-switching role requiring strong autonomy and decision-making capability.
The Tech Environment:
Target Stack
React (TypeScript) React Navigation Reanimated
Legacy / Stack
100% Kotlin Android SDK 24–34 Jetpack Coroutines (Flows/Channels) Koin (Dependency Injection) MockK Gradle Kotlin DSL
You are not expected to know every tool immediately, but you must be comfortable operating deeply in both Android and cross-platform React ecosystems.
Requirements
Must Haves
6+ years of mobile engineering experience. Senior-level Kotlin expertise, including Clean Architecture, MVVM, DI (Koin/Dagger), and Coroutines/Flow. Strong React experience beyond UI — including modules, Bridge/JSI, and performance optimisation. Experience integrating React into an existing Android codebase (brownfield experience). Proven experience architecting or significantly contributing to mobile platform migrations. Comfortable making architectural trade-offs in high-risk, live environments. Ability to manage ambiguity and switch context between greenfield and legacy projects. Strong communication skills and experience working in remote, cross-functional teams.
Nice to Haves:
Experience migrating from fully apps to cross-platform solutions. Experience in transport, logistics, or regulated industries. Familiarity with performance profiling tools on Android. Experience working in B2B SaaS environments. Exposure to Swift/iOS architecture (even if not hands-on).
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
1. Screening Call (30 mins) – Recruiter alignment
2. Technical Architecture Discussion – Migration & RN integration deep dive
3. Deep Dive Interview – Engineering & Product
4. Final Culture Conversation – Leadership alignment
Guaranteed Interview Scheme
We’re a Confident employer and we welcome applications from disabled candidates. If you need any adjustments at any stage of the recruitment process, please tell us what would help - we’ll work with you to make the process as accessible as possible.
We also offer a Guaranteed Interview Scheme (GIS) for candidates who consider themselves to have a 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.
If you are interested in applying for this job please press the Apply Button and follow the application process. Energy Jobline wishes you the very best of luck in your next career move.
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Location:
London
Job Type:
FullTime
Category:
Engineer, Senior, Engineering

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