Principal Mobile Engineer

We are hiring two Principal Mobile Engineers to define and build this foundation alongside the existing mobile team. Together, you will own the tech stack decision: native iOS and Android, Flutter, React Native, or a hybrid, and you will shape the platform every product team at Payoneer ships mobile features on top of. The two-Principal structure gives us the capacity to build the platform properly and the optionality to specialize one Principal per native platform if we go that route.

Responsibilities:

• You will own the tech stack decision and the rationale behind it. You will run the evaluation of native (Swift / Kotlin) vs. Flutter vs. React Native vs. hybrid against real constraints: performance, binary size, hiring market, team contribution model, build and release velocity, and long-term maintenance cost. You will make the call jointly with your peer principal, and you will be expected to defend it under scrutiny from engineering, product, and executive leadership.
• You will build the host application foundation. The architecture, the module boundaries, the navigation and lifecycle model, the dependency injection approach, the state management patterns, the threading and concurrency model, the network stack, the persistence layer, the observability and logging backbone, the release and rollout machinery, the testing strategy at every level of the pyramid. Every product team's first impression of mobile at Payoneer will be the abstractions you ship.
• You will define the contribution model that product teams use to deliver features into the host app. Module boundaries, public API surface, lifecycle hooks, dependency policy, build and integration patterns, version compatibility, and the developer experience that makes contributing a feature fast and contributing a bad one hard. You will own the standards every contributing team writes against.
• You will own performance, binary size, startup time, frame rate, memory, and battery as first-class engineering disciplines with measured budgets and gates. You will own crash-free rate and stability as platform commitments. You will own the CI/CD, signing, release, and rollout pipeline for the app, and the observability that makes a production issue debuggable in minutes rather than days.
• You will partner with the Application Foundations Crew and the Cloud Platform Base, DevEx, and Network and Security teams to make sure mobile integrates cleanly with the platform APIs, events, identity, secrets, automation, and the shift-left controls that apply on the mobile side as much as the server side. You will partner with product engineering across the company to bring contributing teams into the platform and keep them productive in it.

Requirements:

• You have ten or more years of mobile engineering experience, and you have built mobile applications from the ground up, not joined them, not iterated on them, but defined the foundation and shipped it to production at scale. You have an honest, scarred view of what mobile platform decisions cost three years after you make them.
• You are deeply expert in at least one of iOS or Android and seriously fluent in the other. On iOS that means Swift, the Swift concurrency model, UIKit and SwiftUI, the Apple toolchain and release process, and the parts of the ecosystem most engineers learn the hard way. On Android, that means Kotlin, coroutines and Flow, the Android lifecycle, Jetpack and Compose, Gradle in earnest, RxJava, where it still lives, and the same hard-won understanding of the ecosystem.
• You understand the cross-platform landscape with the same honesty. You have an opinion on Flutter, KMP, and React Native that goes beyond preference performance characteristics, ceiling, where each shines, where each fails, and the characteristics and recommendation you would make for a fintech app at Payoneer's scale.
• You have built and operated a modular mobile platform before, or something close enough that you understand the trade-offs: how to define module boundaries that survive ten product teams contributing in parallel, how to keep the host app coherent when contributors disagree, how to version a contribution model without breaking everyone, and how to keep the binary lean as the surface grows.
• You think in budgets and measurements. You have driven startup time, frame rate, binary size, and crash-free rate as numbers on a dashboard. You understand mobile observability at a level beyond crash reporting, and you have shipped the instrumentation needed to debug production.
• You communicate clearly with engineers, product partners, and executives. You can write a one-page architecture proposal, run an RFC that actually converges, demo what you built so other engineers want to use it, and explain a stack decision to a CPO in language they care about. You handle disagreement well, including with your peer principal, and you know how to land a joint decision.

Nice to have:

• Experience integrating AI capabilities into mobile applications on-device models, conversational and agent UI patterns, latency-sensitive AI features, and the privacy and offline considerations that come with them is a strong plus, given Payoneer's AI-native platform direction.