Requirements

Let's refine the design of a simplified LinkedIn. This isn't about building a full-fledged social network, but rather focusing on the core interaction: the connection network and the feed. We'll model users, their connections, and how they consume and publish content in their feed. The key is to design this with a focus on scalability, extensibility (imagine adding new content types or feed filtering options), and thread safety (many users interacting concurrently). Think about the core actions a user performs: connecting with other users, posting different types of content (text, image, video), and viewing a personalized feed. The system needs to efficiently manage these connections and generate feeds based on user preferences and network activity. We aim for a design that minimizes coupling between components and promotes code reusability. # Requirements ## Functional Requirements 1. **User Management:** * Ability to create a user profile with basic information (name, ID). * Ability to retrieve user profile information. 2. **Connection Management:** * Ability to send and accept connection requests. * Ability to retrieve a user's connections (list of connected users). * Ability to remove a connection. 3. **Post Management:** * Ability to create different types of posts (TextPost, ImagePost, VideoPost). Each post should have a timestamp, author, and content. * Ability to retrieve a specific post by its ID. 4. **Feed Generation:** * Ability to generate a user's feed, which consists of posts from their connections, ordered by timestamp (newest first). * Ability to filter the feed based on post type (e.g., show only ImagePosts). * Ability to apply a configurable feed ranking/sorting algorithm (e.g., prioritize posts from closer connections, or those with more engagement). 5. **Concurrency**: * Handle concurrent requests for all the above functionalities without data corruption or race conditions. ## Non-Functional Requirements 1. **Thread Safety:** All operations, especially those modifying user connections or post data, must be thread-safe. Consider appropriate synchronization mechanisms (locks, concurrent data structures) to prevent race conditions. 2. **Extensibility:** The system should be easily extensible to support new types of posts (e.g., ArticlePost, PollPost) without modifying existing code extensively. Use design patterns like Strategy, Factory. 3. **Modularity:** The system should be composed of loosely coupled modules, each responsible for a specific aspect of the functionality (e.g., User Management, Connection Management, Post Management, Feed Generation). 4. **Testability:** The system should be designed in a way that allows for easy unit and integration testing of individual components. Dependency Injection could be helpful. 5. **Performance:** Feed generation should be reasonably efficient, even for users with a large number of connections. Consider indexing strategies or caching (if beneficial within the confines of in-memory data). Focus on algorithmic efficiency first. 6. **Maintainability**: The code should be well-documented, easy to understand, and follow coding standards. ## Core Entities 1. **User:** Represents a user of the system. Contains user information (ID, name, etc.) and manages connections. Key responsibility: Managing connections and initiating content creation. 2. **Post:** Abstract base class for different types of posts. Contains common attributes like timestamp, author, and content. Subclasses: TextPost, ImagePost, VideoPost. Key responsibility: Encapsulating post data and type-specific behavior. 3. **ConnectionManager:** Manages user connections. Provides methods for sending/accepting requests, retrieving connections, and removing connections. This could potentially become a bottleneck, so consider how to handle concurrent access. Key responsibility: Managing the graph of user relationships. 4. **Feed:** Represents a user's personalized feed. Contains a list of posts ordered by timestamp. Key responsibility: Aggregating posts from connections and applying filtering/ranking. 5. **PostFactory:** A factory class responsible for creating different types of posts based on input parameters. This promotes the Open/Closed principle, allowing new post types to be added without modifying existing code. Key responsibility: Creating Post objects. 6. **FeedFilter**: Interface or Abstract Class for various feed filters. Concrete filters (e.g., `ImageFilter`, `VideoFilter`) implement the filtering logic. Key Responsibility: defining the contract for filtering feed. 7. **FeedRankingStrategy**: Interface defining a ranking strategy for the feed. Concrete implementations (e.g. `TimeBasedRanking`, `EngagementBasedRanking`) implement the ranking logic. This allows flexible and dynamic feed ranking. Key Responsibility: defining the contract for ranking/sorting feed.

Design LinkedIn.

Requirements

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Functional Requirements

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Non-Functional Requirements

Core Entity Identification

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