Mobile Engineer at Hydrogen Group, City of London, 8 Weeks, £400-£430 per day

My client has a need for an experienced Android Engineer to join their team for an initial 8 week piece of work with potential to extend. This is a hybrid role and is outside of IR35

Android (primary depth)

• Kotlin and modern Android in large production codebases; Jetpack Compose alongside Legacy View-based UI
• Multi-module builds: reading, untangling and mapping them, including convention plugins and version catalogues
• DI frameworks and the ability to derive actual runtime structure from wiring
• Architectural patterns in practice (MVVM, MVI, Clean-style layering), and the ability to identify what a codebase genuinely does

Code archaeology and analysis

• Navigating an unfamiliar large codebase quickly and systematically
• Static analysis, dependency graph extraction, module dependency visualisation, code search at scale
• Reading CI/CD pipelines as a source of architectural truth: Fastlane, Bitrise, GitHub Actions, Jenkins, Gradle/Xcode build logic
• Reconstructing runtime behaviour from instrumentation, logging and observability tooling (Crashlytics, Sentry, Dynatrace, Firebase or similar)

Backend and API

• Tracing a request from UI through the mobile networking layer to the Back End service and back
• REST/GraphQL/gRPC, OpenAPI and contract inspection, API gateway and BFF patterns
• OAuth 2.0/OIDC token flows as implemented on device
• Third-party SDK inventory and assessment: analytics, payments, chat, fraud, marketing, feature flags

Banking-specific mobile concerns

• Secure storage, biometric authentication, device binding, certificate pinning as implemented in code
• Feature flags, remote config, phased/staged rollout, kill switches
• Offline behaviour, caching and state management, and what happens at the edges

Essential non-technical skills

• Structured interviewing - runs a technical interview that yields specifics rather than a tour of opinions, and captures it in a form the team can use
• Rigorous note-taking and traceability - findings can be traced back to a source; distinguishes what was observed in code from what someone said
• Collaborative, non-territorial - will be reviewing other engineers' work in front of them; needs to do it without triggering defensiveness
• Self-directed under time pressure - 8 weeks means little supervision and no ramp-up period
• Fluent professional English, spoken and written

Nice to have

• Financial services or other regulated-sector mobile delivery
• Kotlin Multiplatform, React Native, or hybrid/webview integration experience
• Diagramming from code: Structurizr, PlantUML, Mermaid, dependency-graph tooling
• Accessibility and performance profiling experience
• Consultancy or contracting background with multiple client environments
• iOS working knowledge (second depth) - Swift, SwiftUI/UIKit, SPM and Xcode project structure - sufficient to read the codebase and validate the Architect's iOS findings

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