System Design | Stack Overflow

Designing a system like Stack Overflow includes thinking about diverse elements such as scalability, reliability, and user experience. In this text, we will go through important key components and design selections for developing a scalable and efficient Q&A platform.

Requirements for Stack Overflow

Functional Requirements

• The system must be designed in this sort of way so that the user ought to be able to put up a question and solution easily without any inconvenience.
• The system ought to include functionality through which they must be able to upvote/downvote questions and answers.
• The system needs to make certain that the user can add comments in query and solution.
• The system ought to make certain the consumer is getting notified every time absolutely everyone offers a solution to his question.
• The system must contain a search bar so he can search questions effortlessly.

Non-Functional Requirements

• The system must have Low-latency response times for consumer interactions.
• The system must contain high availability and reliability.
• It must be Scalability to handle a large number of users and content.
• Security measures to protect consumer records and save you unauthorized access.
• Moderation tools to control content and user interactions.

Capacity Estimation for Stack Overflow

You can estimate the system capacity by analyzing certain data like traffic, number of questions asked, number of answers posted, etc. By analyzing whole data we can further calculate the required storage capacity for whole year. Here is the simplified calculation given:

Traffic is 135 million per month

Traffic per second = 135,000,000/30*24*60*60
= 52.08
Assumption- 20% user ask question
20% user answer question

TPS – 20+20 =40
Storage required (approx 100kb/questions) = 40*100 = 4000 KB/S = 4 MB/S
Storage required per year = 4*60*60*24*365 = 125TB

Use Case Diagram for Stack Overflow

Illustrate interactions among actors (users, moderators) and the machine.

Below is the explanation of the above diagram:

• Unregistered User -: Unregistered users (those without an account) have access to search queries, user accounts on Stack Overflow, collaborations, related businesses, and tags.
• Registered User: Users that have registered have accounts, can ask and answer questions, build teams, join teams, follow questions, join collectives, and carry out a few more simple tasks. With increased authority, individuals can add comments, vote a question up or down, set question bounties, make tags and synonyms, remove questions, and more. Higher privileges give access to more capabilities.
• Account owners who are part of a team are considered team members. Within their teams, they are able to both ask and respond to questions. Any external party cannot access anything that occurs within a team.
• Members of a team who have the ability to edit articles and remove team content are considered collaborators.
• Admins are team members with the ability to add and remove team members, activate and deactivate team members, and grant and withdraw access to any registered user.

Low-Level Design (LLD) for Stack Overflow

Low-Level Design includes special design of every module or thing identified all through the High-Level Design. It specializes in how the device may be carried out, protecting factors inclusive of data structures, algorithms, and particular technology. Here’s a breakdown of LLD for key components:

• User Management Module: In the Low-Level Design of the User Management module, meticulous interest is given to user registration, authentication, and profile control. The User magnificence is defined with stable password hashing, and strategies for generating and validating authentication tokens. User Profile details are particular, ensuring a complete technique to user data security and control.
• Question and Answer Module: In the Low-Level Design of the Question and Answer module, the focal point is on granular details like question posting, modifying, and deletion. Classes for Question, Answer, and Comment are defined with techniques tailored for every action. Polymorphic institutions are carried out for feedback, allowing flexibility for each questions and answers. The LLD guarantees robust handling of dynamic user interactions within the Q&A platform.
• Voting and Reputation Module: The Low-Level Design of the Voting and Reputation module delves into the specifics of user voting and popularity calculation. The Vote class is outlined with strategies for upvoting and downvoting, and reputation calculation algorithms are meticulously designed. This exact layout guarantees the accuracy and fairness of the reputation system, a essential thing for user engagement and moderation on Stack Overflow.
• Tagging Module: In the Low-Level Design of the Tagging module, the focus is at the implementation of a flexible tagging system. The Tag magnificence is defined with strategies for adding and removing off tags, and a many-to-many relationship table, QuestionTag, is detailed. Methods for user to observe precise tags are intricately designed, contributing to efficient content company and user customization.

High-Level Design (HLD) for Stack Overflow:

High-Level Design presents an outline of the complete system, define its all the major components . It would not go into the nitty-gritty information but focuses on the relationships between different-different modules. Here’s a simplified HLD for Stack Overflow:

High Level Design

• Web Servers: Web servers, in the High-Level Design, play a primary function in handling HTTP requests and serving static content. Load balancing guarantees most useful traffic distribution throughout multiple internet servers, contributing to more advantageous performance and availability at the Stack Overflow platform.
• Application Servers: Application servers function as the backbone of enterprise logic and consumer authentication. They interact with database servers and control interactions among various modules. Containerization is leveraged for smooth deployment and scaling, presenting a flexible and scalable structure.
• Database Servers: Database servers save numerous information, and the High-Level Design emphasizes optimized queries and efficient indexing for brief data retrieval. Sharding is employed to distribute data, ensuring scalability as Stack Overflow handles an extensive database of user-generated content material.
• Caching Layer: In the High-Level Design, the caching layer is implemented to optimize performance. Frequently accessed data is cached, reducing the weight on database servers and contributing to an ordinary responsive user experience. Effective cache eviction techniques are mentioned to manipulate memory sources successfully.
• Search Engine (Elasticsearch): Elasticsearch is included as the search engine within the High-Level Design, efficaciously indexing and retrieving relevant effects for questions and solutions. Seamless communication with the Search module guarantees that user get quick result when they use search engine.
• CDN (Content Delivery Network): The Content Delivery Network (CDN) is hired to distribute static assets globally inside the High-Level Design. This international distribution reduces latency and enhances the speed of content material delivery, enhance user experience throughout different regions.

Database Design for Stack Overflow

User Table

User table can be designed to store user data. This table include fields:

User_id: A precise identifier for every user.
Display_name: It display name publicly
email_address: User’s email forinformation exchange.
Password: Securely hashed user password.
About_me: description about user.
Location: User’s exact location.
Created_date: Registration date of person

Comment Table

Comment table are designed to store comments of the question. This table include fields like :

Comment_id: Unique identifier for each comment.
Created_by_user_id: Id of the user who created the comment.
Post_id: It is the Id of the associated question or answer.
Comment_text: Text content of the comment.
Created_date: The date on which user have commented.

Post Table

Post table are designed to store post details. It include fields like:

Post_id: Unique identifier for each post.
Created_by_user_id: Id of the person who created the post.
Parent_question_id: Id linking posts to their figure questions.
Post_type_id: The type of put up (question, solution, and so on.).
Accepted_answer_id: The Id of the accepted answer if the post contain a questiom.
Post_title: The name of the post.
Post_details: The targeted content of the post.
Created_date: The date and time when the submit was created.

Vote table

Vote table are designed to store how many upvote and downvote are their on the post. It include fields like:

Vote_id: A unique identifier for every vote.
post_id: The Id of the post (question or answer) on which the vote is cast.
user_id: The user Id of the voter.
vote_type_id: The type of vote (upvote or downvote).

Tag table

Tag table are designed to store tags. It include field like:

tag_id: A unique identifier for every tag.
tag_name: It describe the name of the tag.
tag_description: It give full description providing all the information about the tag.

Scalability for Stack Overflow

• Web Servers: In the web servers layer of Stack Overflow, scalability is achieved via horizontal scaling. Multiple instances of internet servers are deployed at the back of a load balancer, making sure even distribution of incoming site visitors. This approach permits the device to deal with a developing variety of concurrent user seamlessly. Additionally, the implementation of auto-scaling mechanisms permits dynamic changes to the wide variety of net server instances primarily based on demand, making sure optimal resource usage all through varying workloads.
• Application Servers: Scalability inside the application servers layer is facilitated with the aid of containerization technologies including Docker. These technology allow for the packaging and deployment of programs continuously across numerous environments, contributing to scalability and versatility. Auto-scaling mechanisms further enhance this accretion, allowing the system to adapt to changing demands effectively. The use of containerization ensures that programs run constantly, promoting a scalable and streamlined structure.
• Database Servers: Within the database servers layer, scalability is addressed through sharding and using read replicas. Sharding includes the horizontal partitioning of statistics throughout more than one database servers, preventing any single database from becoming a performance bottleneck. Read replicas are applied to deal with read-intensive operations, taking into consideration parallel processing of queries and decreasing the burden at the number one database server. These techniques together make contributions to the scalable storage and retrieval of data.
• Caching Layer: The caching layer is a vital thing for scalability in Stack Overflow. By enforcing a distributed caching system, which include Redis or Memcached, often accessed data is stored throughout more than one nodes. This method enhances horizontal scalability via distributing the cache load, improving response times, and lowering the pressure on the primary servers. Effective cache eviction strategies also are in region to manipulate reminiscence resources efficaciously, making sure optimum performance.

Microservices and API Used for Stack Overflow

The following technologies were employed in the development of Stack Overflow:

ASP.NET MVC

Web development framework that is lightweight and highly efficient, supporting C#, F#, Visual Basic, and C++. Among this framework’s characteristics are:

• Model validation: Data annotation validation attributes are used to do model validation. Values are posted to the server after validation attributes have been verified.
• Dependence Injection: adheres to clear dependence rules, permits the registration of dependent logic to enhance code maintainability, decrease class coupling, promote class reusing, and enhance application testing
• Cross-platform: Cross-platform application development: programs created with ASP.NET run on multiple platforms, including Mac OS and GNU/linux, in addition to Windows.

Visual studio IDE

Visual studio IDE includes web development and ASP.NET MVC components. Provide resources to make C# coding simple. It is also highly extensible.

Microsoft SQL database

Microsoft created and introduced the relational database management system known as SQL Server.

• It comes with Microsoft’s proprietary Transact-SQL language, which allows for the declaration of variables, exception handling, and store procedures, in addition to SQL.
• Users do not need to change the software in order to secure and encrypt data using SQL Server’s improved speed.

Because SQL Server is very safe and employs advanced encryption techniques, it is challenging to penetrate its security levels.

JQuery

A JavaScript package for creating dynamic websites Common activities like modifying a webpage, reacting to events, obtaining data from services, creating effects and animations, etc. are made incredibly simple and uncomplicated using jQuery.

API Code Implementation for Stack Overflow

User Registration API (POST):

• Endpoint: /api/user/register
• Description: Allows users to create accounts securely.

Request: POST /api/user/register

Host: your-stack-overflow-api.com
Content-Type: application/json{
“username”: “example_user”,
“email”: “user@example.com”,
“password”: “securepassword123”
}

Response:

{
“status”: “success”,
“message”: “User registration successful”,
“user_id”: “123456”
}

Retrieve User Details API (GET) Request:

• Endpoint: /api/user/details?user_id=98765
• Description: It retrieve all user data.

Requests:

GET /api/user/details?user_id=98765
Host: design-stackoverflow-api.com
Accept: application/json

Response:

{
“user_id”: “98765”,
“username”: “example_user”,
“email”: “user@example.com”,
“registration_date”: “2023-01-15”,
“profile”: {
“bio”: “Software developer passionate about coding.”,
“reputation”: 1500
}
}

Update Answer API (PUT) Request:

• Endpoint: /api/questions/12345/answers/67890
• Description: It is use to update question and answer data.

Requests:

PUT /api/questions/12345/answers/67890

Host: your-stackoverflow-api.com
Content-Type: application/json
Authorization: Bearer your_access_token
{
“answer_text”: “This is an updated answer to the question.
}

Response:

{
“status”: “success”,
“message”: “Answer updated successfully”,
“answer_id”: “67890”,
“updated_at”: “2023-02-20T14:30:00Z”
}

Conclusion

Designing a system like Stack Overflow requires careful consideration of various components and functionalities to make certain scalable and efficient model. By understanding this article you easily Design Stack Overflow.