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Senior IOS Engineer

Job Information:

Work Experience: 7+ Years
Industry: IT Services
Job Type: FULL TIME
Location: Tokyo, Japan

Role Overview:

We’re looking for a hands-on Senior iOS Engineer to shape the end-to-end architecture of our large-scale mobile platform. You’ll define backend service contracts, data models and client-side frameworks—then own the implementation, debugging, profiling and performance tuning that delivers rock-solid experiences to millions of users. You’ll work closely with Product, Design and Backend teams to drive technical direction and mentor a growing iOS squad.

Key Responsibilities:

  • Architect and build modular, maintainable iOS apps using Swift, modern patterns (MVVM, Clean Architecture, VIPER, Coordinator) and SwiftUI/Combine or RxSwift.
  • Collaborate on backend API design (REST), data schemas and authentication flows to meet mobile requirements.
  • Lead the design of scalable, event-driven microservices and data pipelines that power your client-side features.
  • Own app performance: use Xcode Instruments (Time Profiler, Allocations, Leaks, Network), os_signpost, Instruments.
  • Automation and custom logging to diagnose and resolve CPU, memory, storage and networking bottlenecks.
  • Establish and enforce code quality standards, automated linting (SwiftLint), static analysis and security scanning (SonarQube, Danger, SecureHeaders).
  • Build and maintain CI/CD pipelines (GitHub Actions) for automated builds, unit/UI tests and phased rollouts via TestFlight.
  • Mentor mid-level engineers on best practices for TDD, observability (Crashlytics, Firebase Analytics) and architectural reviews.
  • Troubleshoot complex production issues, conduct root-cause analysis and implement long-term fixes and performance monitoring dashboards.
  • Contribute to technical documentation, API specs, design reviews and architectural roadmaps.

Minimum Qualification:

  • Bachelor’s degree in computer science or related technical discipline.
  • 7+ years of professional iOS development experience in Swift/Objective-C.
  • Deep understanding of iOS frameworks, app lifecycle, memory management (ARC), threading (GCD, OperationQueue) and background execution (URLSession, BGTask).
  • Proven track record building large-scale apps (100K+ DAU) with high stability and responsiveness.
  • Expertise in debugging and profiling tools: Xcode Instruments (Time Profiler, Allocations, Leaks, Network), Crash Reports, LLDB.
  • Strong background in RESTful API integration, offline persistence (Core Data, Realm, SQLite).
  • Solid grasp of modern architecture patterns (MVVM, VIPER, Clean Architecture), dependency injection (Swinject, Resolver) and modular codebases.
  • Comfortable working in an Agile environment.
  • Hands-on with building CI/CD, containerization (Docker).
  • Excellent communication skills, ability to drive technical decisions and simplify complex problems for cross-functional teams.

Preferred Qualification:

  • Prior experience as a technical lead or architect in an Agile/Scrum environment.
  • Familiarity with SwiftUI, Combine, async/await and Apple’s modern concurrency model.
  • Exposure to cross-platform frameworks (Flutter, React Native) or Kotlin Multiplatform Mobile.
  • Knowledge of mobile security best practices (Keychain, biometrics, SSL-pinning, encryption).
  • Experience with A/B testing and feature-flagging platforms (Firebase Remote Config, LaunchDarkly).
  • Open-source contributions to iOS libraries or public speaking/blogging on iOS topics.