Mobile Application Architecture

November 27, 2022 7:00 PM PST

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This meeting focused on the architecture of mobile applications, discussing requirements, system design, and best practices for mobile system design interviews. Key topics included user flow, data flow, and various architectural patterns, as well as considerations for scalability and offline support.

Presenter: Yi, Tech Lead

Agenda

1. Requirements
2. System Design
3. Wrap-up
4. Mobile System Design Interview Tips

Mobile System Design Interview Tips

• Gather requirements within 10 minutes
• Make decisions collaboratively

Steps in System Design

1. Requirement Gathering
2. High-Level Design
3. API Design
4. Implementation Design

Requirements

Functional Requirements

• List of chat windows
• Send and receive messages

Non-Functional Requirements

• Start with support for 10,000 users, scalable to 100 million users
• Offline support
• Memory and battery efficiency

High-Level Design

Mobile Architecture Patterns

• MVC: Model-View-Controller (traditional)
• MVP: Model-View-Presenter

Navigation

• Navigation between app screens using a navigator

Data Sources

• Chat application data sources:
  • HTTP GET
  • WebSocket
  • Key/Value data
  • Files
  • Local Database
  • In-memory storage

HTTP Methods

• GET, POST
• Polling:
  • Short polling: one-time query
  • Long polling: bi-directional communication (resource-intensive)

Data Handling

GraphQL and Pagination

• Offset pagination: GET /feed?after=2021-05-25T
• Keyset pagination: GET /feed?after_id=t1234xyz&limit
• Cursor pagination for efficient data retrieval

Push Notifications

• Can wake up the application in the background
• Difference between notifications and WebSocket:
  • WebSocket is active while the app is running
  • Notifications are used when the app is not running

Offline Support

• Local cache as a data source
• Key-value data storage
• Mobile database considerations

Security

Encryption

• WebSocket encryption at various layers
• File encryption using built-in mechanisms from mobile platforms
• Considerations for images and sound files

User Interaction

WebSocket Management

• Handling offline and online states with WebSocket connections
• Efficient management of WebSocket connections for multiple users

User Flow and Experience

• Steps and states in user interaction
• Data flow between network, business model, and view

Component Architecture

• Challenges in specific components
• Strategies for real-time updates and caching to improve user experience
• View reuse for performance enhancement

Team Collaboration

Modularization

• Unit testing for different features
• Common libraries and dependencies
• Structure of the main application and features

Questions and Answers

• Mobile Push Notifications: How do they work?
• Comparison to Text Messages: Similarities in functionality

This structured approach ensures a comprehensive understanding of mobile application architecture, focusing on scalability, user experience, and technical considerations.