Grokking Modern Mobile System Design Interview
The mobile system design interview, for iOS and Android engineers. You design the client: the layers, the data flow, offline behaviour, and what the user sees when things fail.
Course Overview
Most system design preparation teaches you to design a server. A mobile design round asks for something else. The backend is usually given to you in one sentence, and the whole interview is about the app on the device. This course covers that round end to end. It starts with how the round is graded and the five step method to answer any mobile system design question that fits in 45 minutes. It then goes deep on the material interviewers actually push on: client architecture, API design for a bad network, storage and offline behaviour, performance and device limits, security, and how a mobile feature ships. It closes with library design questions, sixteen full case studies, and a playbook of what to say. Every lesson serves both platforms. The prose stays neutral and a small table gives the iOS and Android name for each mechanism.
What you'll learn in Grokking Modern Mobile System Design Interview
- A repeatable five-step method for answering mobile system design questions, clarifying requirements, and explaining your design choices.
- Offline-first design: local storage, caching, synchronization, conflict resolution, and recovery of saved work after an app restart.
- How to improve startup, scrolling, image loading, and video playback while managing memory, battery, and network use.
- Step-by-step case studies covering news feeds, chat, photo backup, food delivery, checkout, ride hailing, and on-device AI assistants.
- How to design client architectures for iOS, Android, and cross-platform apps, with clear responsibilities and data ownership.
- How to design API contracts, pagination, real-time updates, and safe retries when requests fail or responses are lost.
- Practical security and release decisions: authentication, account isolation, protected storage, feature flags, testing, and monitoring.
- How to design reusable libraries and SDKs for image loading, file transfers, networking, analytics, feature flags, and push notifications.
Course Content
Scoping and Requirements for a Mobile Feature
Client Architecture
Introduction: Client Architecture
The Four Layers of a Mobile App
Choosing an Architecture Pattern
Unidirectional Data Flow in SwiftUI and Compose
The Single Source of Truth
Dependency Injection and Testing
Modularization and App Size
Navigation, Deep Links, and State Restoration
Drawing the Architecture Diagram
Native vs Cross Platform
Capstone: Designing a Product Screen
Assessment: Client Architecture
Offline, Sync, and Storage
Introduction: Storage, Caching, and Offline
On Device Storage Options
The Client Data Model
Caching, Eviction, and Invalidation
Offline First
Background Execution
Optimistic Writes and the Outbox
Delta Sync
Sync and Conflict Resolution
Local Schema Migrations
Capstone: Offline Notes With Sync
Assessment: Offline, Sync, and Storage
Security, Shipping, and Operating
App Case Studies I: Feeds, Messaging, and Commerce
Performance, Media, and Real-Time
Introduction: Performance, Media, and Real-Time
App Startup
Lists, Images, and Memory
Threading With Swift Concurrency and Coroutines
Battery, Data, and Low End Devices
Stories and Short Video
Ride Hailing
Stock Tickers and Live Comment Streams
On Device AI Assistant
Capstone: Fixing a Slow Feed
Assessment: Performance, Media, and Real-Time
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About the Author
Arslan Ahmad
Industry Expertise & Leadership
Arslan Ahmad is the lead author of Grokking Modern Mobile System Design Interview. As the founder of Design Gurus and a former FAANG hiring manager, he has worked at industry giants like Facebook (now Meta) and Microsoft.
He has conducted hundreds of system design interviews, giving him unique insight into what top tech companies look for in candidates.
The course also incorporates expertise from senior engineers at Google, Meta, Amazon, Microsoft, and Uber, ensuring you learn system design best practices from professionals who have built and scaled real-world systems.
500+
Interviews Conducted
10k+
Students Taught
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