Senior Mobile Engineer (Swift and/or Kotlin)

Employment: Contract Experience: Mid-Senior level Exerizon is a fast-growing strategy and technology consulting firm founded by former senior leaders from global consulting and cloud organizations. We help current and future market leaders tackle their greatest challenges — from digital strategy and cloud transformation to data & AI platforms and application modernization. We redefined the traditional consulting model: we share risk with our clients through impact-based remuneration, and we share ownership with our people from day one. We are looking for a Senior Mobile Engineer to build and modernise native mobile apps for our clients in banking, insurance and healthcare — on iOS ( Swift ), Android ( Kotlin ), or both. You will work on apps that are the client's primary customer channel: high traffic, strict security and regulatory requirements, and real consequences when a release goes wrong. What you will do: Design and build native apps in Swift (SwiftUI, UIKit) and/or Kotlin (Jetpack Compose) — new features, modernisation of legacy codebases, and rewrites where they are justified Own the architecture on your platform: modularisation, MVVM / Clean Architecture / TCA, dependency injection, offline-first and data sync strategies Build and evolve server-driven UI (SDUI) : design component schemas with backend teams (JSON or Protobuf), own the client-side rendering engine, handle schema versioning, backward compatibility and graceful fallbacks — so product teams ship new journeys without an app release Practise AI-driven development every day: coding agents and copilots (Claude Code, Cursor, GitHub Copilot) for implementation, refactoring, test generation and code review — with the judgement to verify and own what they produce, and the discipline to bring that practice to the whole team Integrate with backend services (REST, GraphQL, gRPC) and secure the app end to end: OAuth2 / OIDC, biometrics, secure storage (Keychain, Keystore), certificate pinning, root and jailbreak detection, OWASP MASVS Set and enforce engineering standards: code review, unit, UI and snapshot tests, CI/CD (Fastlane, GitHub Actions, Azure DevOps or Bitrise), signing, App Store and Google Play release management with phased rollouts Build in observability and product quality: crash reporting, analytics, feature flags, performance and startup-time budgets Deliver accessibility (WCAG 2.2 / EN 301 549) and localisation to the standard regulated clients require Work directly with client product owners, designers, backend engineers and QA; estimate, plan and demo your work to stakeholders Mentor mid-level engineers, raise the bar across Exerizon's mobile practice, and support proposals and pre-sales demos Requirements 6+ years of native mobile development, including 3+ years in Swift (iOS) and/or Kotlin (Android); at least two apps shipped to production and maintained through multiple releases Deep knowledge of your platform — iOS: SwiftUI and UIKit, Swift Concurrency or Combine, Xcode toolchain; Android: Jetpack Compose, Kotlin Coroutines and Flow, Android Jetpack, Gradle — with a working understanding of the other platform Hands-on experience with mobile security in regulated environments: OAuth2 / OIDC and strong customer authentication flows, secure storage, certificate pinning, OWASP MASVS, and closing pen-test findings Solid testing and CI/CD practice: XCTest or JUnit, UI and snapshot tests, automated pipelines, code signing, store submission and release management Proven ability to own architecture decisions and refactor large legacy codebases safely, with measurable improvements in build time, crash rate or release cadence Experience designing or integrating a server-driven UI framework: component schemas, a client renderer, schema versioning and A/B-tested layouts; you know where SDUI pays off and where it hurts (offline, performance, accessibility) AI-driven development as part of your workflow: you use coding agents and copilots daily, understand their failure modes, and review AI-generated code to the same standard as your own Fluent in API integration: REST and GraphQL, OpenAPI contracts, and working with backend teams on API design Experience delivering apps in banking, insurance, fintech or healthcare, including PII handling and regulatory constraints (PSD2 / SCA, GDPR) Clear communication with non-engineers: you explain trade-offs to a product owner and estimate honestly Full professional fluency in Polish and English Nice to have: Mobile payments integration (Apple Pay, Google Pay, BLIK) Accessibility auditing experience (VoiceOver, TalkBack) Tech lead or team lead experience on a client-facing engagement Building your team's AI tooling: custom agents, MCP servers or codebase-specific skills and prompts Shipping an SDUI-based app at scale, or contributing to an open-source SDUI framework Benefits Real ownership of the apps you build and direct contact with client product owners — no ten-layer review pyramid Competitive compensation on B2B contract Annual training and certification budget Remote work model with access to a central Warsaw office A seat at the table in shaping a young firm: our mobile practice, engineering standards, hiring and culture