Mobile Systems Engineer (Android + iOS)

Location: OnSite/Hybrid/Remote
Team: Work closely with Backend, Security, QA, Product Partners: Cryptography/Wallet team, API/Backend teams, Platform/SRE

About us

We build secure, high-performance mobile components for financial and crypto-native products. Our mobile stack includes Kotlin (Android), Swift (iOS), and performance-critical native C++ libraries (NDK/JNI on Android; Swift/ObjC++ bridging on iOS). The focus of this role is “backend-like” mobile engineering: cryptographic flows, secure key storage, hardened networking, native library integration, reliability, and automation — not UI feature work.

We’re looking for a senior engineer who can own mobile systems end-to-end: integrating native C++, Rust components, designing secure workflows, building robust service layers, and shipping reliably with strong testing and CI/CD.

What you’ll do

● Own mobile systems architecture (Android + iOS): design and implement non-UI core modules used by the apps.

● Native C++ integration: integrate/extend C++ libraries for cryptography/signing; maintain build toolchains (CMake, Gradle NDK, Xcode); manage ABI compatibility and performance.

● Mobile-to-native bridging:

○ Android: JNI/NDK integration and Kotlin APIs

○ iOS: Swift ↔ ObjC/ObjC++ bridging and Swift-friendly APIs

● Secure mobile development: implement keystore/keychain usage, secure enclaves/secure hardware flows where applicable, secret handling, certificate management, and secure networking (mTLS).

● Transaction/signing flows: build reliable signing request lifecycle, idempotency, retries, state machines, and audit-friendly event logs (without leaking sensitive data).

● Networking & data layer: implement resilient networking (REST/WebSockets/gRPC/Noise where applicable), serialization, caching, offline-safe queueing, and background execution constraints.

● Hardening & integrity: contribute to tamper resistance, runtime integrity checks, attestation/integrity signals where applicable, and secure update/rollout practices.

● Observability & reliability: crash/ANR monitoring, structured logging, performance profiling, and regression prevention.

● CI/CD & releases: build pipelines for Android/iOS (signing, packaging, automated tests), reproducible builds, and fast feedback loops.

● AI-assisted engineering: use Cursor (or similar) for code generation/refactors/tests, with rigorous review, security checks, and deterministic builds.

Must-have experience

● 6+ years in mobile engineering with significant depth in “systems” work (not primarily UI)

● Strong Kotlin (Android) and strong Swift (iOS) for core modules / service layers

● Solid C++ experience, including integrating native libraries into mobile apps

○ Android NDK/JNI and iOS ObjC++/Swift bridging

● Practical mobile security engineering experience: keystore/keychain, secure storage, TLS/mTLS, certificate handling, secure secret handling

● Strong networking fundamentals: REST, WebSockets, TLS, serialization, retries, idempotency

● Build/tooling expertise: Gradle, CMake, NDK toolchains, Xcode build settings, dependency management

● CI/CD ownership: GitHub Actions/GitLab CI, Fastlane, signing & release workflows

● Strong debugging and performance profiling skills across layers (app ↔ native ↔ network)

● REQUIRED: regular use of AI coding tools (Cursor / Copilot / similar) to accelerate delivery (codegen, refactors, tests), with disciplined verification, code review, and

security awareness

Nice to have

● Crypto wallet / MPC / signing systems exposure

● gRPC/Protobuf, binary serialization, performance-oriented networking

● Mobile attestation / integrity signals / anti-tampering practices

● Experience in regulated environments (fintech, custody, payments)

● Kotlin Multiplatform (KMM) or shared native core libraries used by both platforms

● Open-source contributions in mobile/native/crypto ecosystems

Soft skills

● Ownership mindset: accountable for correctness, security, performance, and delivery

● Strong collaboration with backend/security teams; clear written communication

● Pragmatic approach: balances ideal solutions with time-to-market

● Automation-first: tests, CI, and tooling improvements are part of the job

● Comfortable with AI-assisted workflows: prompt discipline, verification habits, and maintaining deterministic builds

● Comfortable working in high-velocity and ambiguous environments

What this role is NOT

● Primarily building UI screens or pixel-perfect layouts

● Primarily React Native / frontend mobile feature development