System Design Ready
Next: Chat App Design

Master iOSSystem Design

The complete iOS interview preparation platform. Practice real system design questions with Swift solutions, senior-level feedback, and proven patterns.

Swift
System Design
Architecture
Performance
Concurrency

What is a combine?

In pro sports, a combine is where athletes perform standardized drills to demonstrate their core abilities, like the NFL Combine.

We've brought this concept to iOS interviews — measuring fundamental engineering capabilities through consistent, practical challenges.

LOADINGLOADINGLOADINGLOADING
INITIAL SCROLL
WEAK YES
Defined pagination APIs but did not discuss tradeoffs.
FEATURED CHALLENGE
Build a Chat App
Design a chat app focusing on offline support, message sync, and clean architecture. Common in iOS interviews at messaging companies.
Chat Application System DesignFunctional Requirements:• Real-time message sync• Offline support• Read receipts• Media attachmentsAPI Routes:• GET /chats• GET /chats/:id/messages• POST /messages• WS /chat-updatesChat List ViewChat Detail ViewView ModelsRepositoriesCore DataTechnical Considerations:• MVVM + Coordinator Pattern• SQLite + Core Data for persistence
Design Review
Technical Analysis
DESIGN FEEDBACK
Endpoints are clean and well-documented ✓
No clear strategy for syncing when offline →

Real Mobile Interview Practice

Practice with an experienced mobile engineer. Focus on what actually comes up: architecture patterns, performance, and practical implementation details.

1

Pick Your Challenge

Start with real interview questions: build a chat app or video uploader. Focus on architecture and implementation details.

Chat AppVideo Upload
2

Architecture Discussion

Walk through your approach with real interview questions about state management, offline support, and error handling.

INTERVIEWER

"How would you handle message delivery status? Consider offline scenarios and sync."

3

Implementation Details

Deep dive into iOS/Android specifics: memory management, background states, and platform patterns.

Memory & State Management
Background Sync Strategy
CURRENT INTERVIEW
Chat App Architecture
IN PROGRESS
INTERVIEWER

"How would you handle memory for image attachments? What happens when the user scrolls through a long chat history?"

FEEDBACK
Good use of NSCache/LRUCache
Consider prefetch on scroll
COMING UP

Let's discuss background state handling and push notifications