Introduction:
Welcome to New Post: How to Design Twitter: A Low-Level System Design Guide
Twitter (x) is one of the most popular social media platforms, handling billions of users and tweets daily. Designing such a system involves addressing scalability, performance, and reliability while keeping the core functionality simple and efficient. This blog breaks down the Low-Level Design (LLD) of Twitter to help you understand how such a system can be built.
What We’ll Cover:
1. Core Requirements of Twitter.
2. Key Components in the Design.
3. Database Design for Scalability.
4. Step-by-Step Workflow of Key Features.
5. Challenges and Solutions.
1. Core Requirements of Twitter:
Before diving into the design, let’s outline the key features Twitter offers:
Functional Requirements:
- Users can create, edit, and delete tweets.
- Users can follow/unfollow other users.
- A personalized timeline displays tweets from followed users, sorted by time.
- Support for hashtags, retweets, and likes.
- Search functionality for tweets or users.
Non-Functional Requirements:
- High Availability: The platform should always be accessible.
- Low Latency: Tweets and timelines should load quickly.
- Scalability: Handle millions of active users simultaneously.
2. Key Components in the Design:
Twitter’s system can be broken down into the following:
Frontend:
- Web and mobile applications to interact with the backend.
- Uses APIs for all operations.
Backend Services:
- User Service: Handles user registration, login, and profile management.
- Tweet Service: Manages tweet creation, deletion, and metadata (likes, retweets).
- Follow Service: Tracks relationships between users.
- Timeline Service: Generates personalized timelines for users.
Storage and Caching:
1. Databases:
- SQL Databases: For structured user and tweet data.
- NoSQL Databases: For flexible and scalable data storage, like user timelines.
2. Caching:
- Redis or Memcached to store frequently accessed data (e.g., recent tweets)
Search Engine:
Use Elasticsearch to enable full-text search for tweets and hashtags.
Message Queue:
Use Kafka to handle asynchronous processes, like timeline updates and notifications.
3. Database Design for Scalability:
User Table:
| Column | Type | Description |
| UserID | Primary key | Unique identifier for users. |
| Name | String | Display name. |
| String | User’s email address. |
Tweet Table:
| Column | Type | Description |
| TwitterID | Primary key | Unique identifier for tweets. |
| UserID | Foreign Key | Owner of the tweet. |
| Content | Text | Text of the tweet. |
| TimeStamp | DateTime | Time the tweet was posted. |
Follow Table:
| Column | Type | Description |
| UserID | Foreign Key | User who is following. |
| FolloweeID | Foreign Key | User being followed. |
4. Step-by-Step Workflow of Key Features:
Posting a Tweet:
- User submits a tweet via the frontend.
- Backend validates and stores the tweet in the Tweet Service database.
- A message is sent to Kafka to update the timelines of followers asynchronously.
Generating a Timeline:
- Pull Model: When a user opens their timeline, the backend fetches recent tweets from followed users.
- Push Model: When a user posts a tweet, the system pushes the tweet to followers’ timelines.
- Cache frequently accessed timelines for faster retrieval.
Follow/Unfollow
- When a user follows/unfollows another, the Follow Service updates the graph database.
- Timeline Service adjusts the content fetched for the follower.
5. Challenges and Solutions:
Challenge 1: Handling High Read/Write Traffic
- Solution: Use caching for popular timelines and tweets. Distribute read/write requests across multiple servers using sharding.
Challenge 2: Scalability of Timelines
Solution:
- Use a fan-out model to update timelines asynchronously.
- Store timelines in a distributed database for fast access.
Challenge 3: Search and Indexing
- Solution: Implement Elasticsearch to provide fast and accurate search results for tweets, hashtags, and users.
Read More:
Best Scenario Based Interview Questions on High Level System Design[Answered]
Best Scenario Based Interview Questions On Low Level System Design [Answered]
Conclusion:
Designing Twitter involves balancing simplicity with scalability and reliability. While the system architecture can be complex, breaking it into modular services makes it manageable. Understanding these building blocks will not only help you design Twitter but also other large-scale systems like Facebook or Instagram.