Design Stack Overflow - Low Level Design

Class Diagram

A class diagram is a graphical representation of the classes, interfaces, and objects in a system and the relationships between them. A class diagram is a blueprint for creating objects and can be used to visualize and understand the design of a system.

This low-level design of Stack Overflow platform code features a variety of classes that work together to provide a comprehensive experience for users. The main classes include Account, Notification, Badge, Photo, Bounty, Comment, Answer, Tag, and Question.

The Account class allows for four types of accounts - Guest, Member, Admin, and Moderator. Members can ask questions and earn a reputation, while Notifications can be sent to members, and Badges can be assigned to them.

The Question class is central to the platform and includes properties such as title, description, view count, vote count, status, closed remarks, answers, comments, tags, photos, badges, and a bounty.

The Answer class is also crucial, with properties such as text, the Account that posted it, view count, vote count, accepted status, comments, and photos.
In the main function, a Member account is created, and a Notification is sent, along with the assignment of a Badge. The creation of a Question and Answer is also demonstrated, with various properties of the Question and Answer being set.

Use Case Diagram

A use case diagram is a visual representation of the interactions between the system, actors, and use cases within a software application. It provides a high-level view of the requirements and helps to identify the goals of the system. Use case diagrams are widely used in software development as they help to communicate the functionality of the system to stakeholders in a clear and concise manner.

Code in C++

#include <iostream>
#include <vector>
#include <string>

class Account {
public:
  enum AccountType {
    GUEST,
    MEMBER,
    ADMIN,
    MODERATOR
  };

  Account(std::string name, AccountType type) : name_(name), type_(type) {}

  void SearchAndViewQuestions() const {
    std::cout << name_ << " is searching and viewing questions.\n";
  }

  void AskQuestion() const {
    std::cout << name_ << " is asking a question.\n";
  }

  void EarnReputation(int reputation) const {
    std::cout << name_ << " earned " << reputation << " reputation.\n";
  }

  std::string GetName() const {
    return name_;
  }

private:
  std::string name_;
  AccountType type_;
};

class Notification {
public:
  Notification(Account& account) : account_(account) {}

  void SendNotification() const {
    std::cout << "Notification sent to " << account_.GetName() << ".\n";
  }

  void AssignBadge(int reputation) const {
    std::cout << "Badge assigned to " << account_.GetName() << " with " << reputation << " reputation.\n";
  }

private:
  Account& account_;
};

class Badge {
public:
  Badge(std::string name, std::string description)
  : name_(name), description_(description) {}

  std::string name_;
  std::string description_;
};

class Photo {
public:
  Photo(std::string file_name) : file_name_(file_name) {}

  std::string file_name_;
};

class Bounty {
public:
    Bounty(){}
    Bounty(int reputation, std::string expiry_date)
        : reputation_(reputation), expiry_date_(expiry_date) {}

    int reputation_;
    std::string expiry_date_;
};

class Comment {
public:
  Comment(std::string text) : text_(text), view_count_(0), vote_count_(0), flag_count_(0) {}

  std::string text_;
  int view_count_;
  int vote_count_;
  int flag_count_;
};

class Answer {
public:
  Answer(std::string text, Account& account) : text_(text), account_(account), view_count_(0), vote_count_(0), flag_count_(0), accepted_(false) {}

  std::string text_;
  Account& account_;
  int view_count_;
  int vote_count_;
  int flag_count_;
  bool accepted_;
  std::vector<Comment> comments_;
  std::vector<Photo> photos_;
};

class Tag {
public:
    Tag(std::string name, std::string description)
    : name_(name), description_(description), daily_frequency_(0), weekly_frequency_(0) {}

    std::string name_;
    std::string description_;
    int daily_frequency_;
    int weekly_frequency_;
};

class Question {
public:
    Question(std::string title, std::string description, Account& account)
        : title_(title), description_(description), account_(account), view_count_(0), vote_count_(0), status_("open"), closed_remarks_("") {}

    std::string title_;
    std::string description_;
    Account& account_;
    int view_count_;
    int vote_count_;
    std::string status_;
    std::string closed_remarks_;
    std::vector<Answer> answers_;
    std::vector<Comment> comments_;
    std::vector<Tag> tags_;
    std::vector<Photo> photos_;
    std::vector<Badge> badges_;
    Bounty bounty_;
};


int main() {
    Account member("Suraj", Account::MEMBER);
    member.AskQuestion();
    member.EarnReputation(100);

    Notification notification(member);
    notification.SendNotification();
    notification.AssignBadge(200);

    Question question("What is Stack Overflow?", "Can someone explain what #include <iostream>
#include <vector>
#include <string>

class Account {
public:
  enum AccountType {
    GUEST,
    MEMBER,
    ADMIN,
    MODERATOR
  };

  Account(std::string name, AccountType type) : name_(name), type_(type) {}

  void SearchAndViewQuestions() const {
    std::cout << name_ << " is searching and viewing questions.\n";
  }

  void AskQuestion() const {
    std::cout << name_ << " is asking a question.\n";
  }

  void EarnReputation(int reputation) const {
    std::cout << name_ << " earned " << reputation << " reputation.\n";
  }

  std::string GetName() const {
    return name_;
  }

private:
  std::string name_;
  AccountType type_;
};

class Notification {
public:
  Notification(Account& account) : account_(account) {}

  void SendNotification() const {
    std::cout << "Notification sent to " << account_.GetName() << ".\n";
  }

  void AssignBadge(int reputation) const {
    std::cout << "Badge assigned to " << account_.GetName() << " with " << reputation << " reputation.\n";
  }

private:
  Account& account_;
};

class Badge {
public:
  Badge(std::string name, std::string description)
    : name_(name), description_(description) {}

  std::string name_;
  std::string description_;
};

class Photo {
public:
  Photo(std::string file_name) : file_name_(file_name) {}

  std::string file_name_;
};

class Bounty {
public:
    Bounty(){}
    Bounty(int reputation, std::string expiry_date)
        : reputation_(reputation), expiry_date_(expiry_date) {}

    int reputation_;
    std::string expiry_date_;
};

class Comment {
public:
  Comment(std::string text) : text_(text), view_count_(0), vote_count_(0), flag_count_(0) {}

  std::string text_;
  int view_count_;
  int vote_count_;
  int flag_count_;
};

class Answer {
public:
  Answer(std::string text, Account& account) : text_(text), account_(account), view_count_(0), vote_count_(0), flag_count_(0), accepted_(false) {}

  std::string text_;
  Account& account_;
  int view_count_;
  int vote_count_;
  int flag_count_;
  bool accepted_;
  std::vector<Comment> comments_;
  std::vector<Photo> photos_;
};

class Tag {
public:
    Tag(std::string name, std::string description)
    : name_(name), description_(description), daily_frequency_(0), weekly_frequency_(0) {}

    std::string name_;
    std::string description_;
    int daily_frequency_;
    int weekly_frequency_;
};

class Question {
public:
    Question(std::string title, std::string description, Account& account)
        : title_(title), description_(description), account_(account), view_count_(0), vote_count_(0), status_("open"), closed_remarks_("") {}

    std::string title_;
    std::string description_;
    Account& account_;
    int view_count_;
    int vote_count_;
    std::string status_;
    std::string closed_remarks_;
    std::vector<Answer> answers_;
    std::vector<Comment> comments_;
    std::vector<Tag> tags_;
    std::vector<Photo> photos_;
    std::vector<Badge> badges_;
    Bounty bounty_;
};




int main() {
    Account member("Suraj", Account::MEMBER);
    member.AskQuestion();
    member.EarnReputation(100);

    Notification notification(member);
    notification.SendNotification();
    notification.AssignBadge(200);

    Question question("What is Stack Overflow?", "Can someone explain what Stack Overflow is?", member);
    question.view_count_ = 50;
    question.vote_count_ = 20;
    question.status_ = "closed";
    question.closed_remarks_ = "Duplicate";
    question.bounty_ = Bounty(100, "2023-02-01");

    Answer answer1("Stack Overflow is a question and answer site for professional and enthusiast programmers.", member);
    answer1.view_count_ = 30;
    answer1.vote_count_ = 15;
    answer1.accepted_ = true;

    Comment comment1("Great answer!");
    comment1.view_count_ = 10;
    comment1.vote_count_ = 5;
    answer1.comments_.push_back(comment1);

    Photo photo1("stack_overflow_photo.jpg");
    answer1.photos_.push_back(photo1);

    question.answers_.push_back(answer1);

    Tag tag1("programming", "Questions related to programming");
    tag1.daily_frequency_ = 100;
    tag1.weekly_frequency_ = 500;

    Badge badge1("Best Answer", "Awarded to the best answer of a question");

    question.tags_.push_back(tag1);
    question.badges_.push_back(badge1);

    std::cout << "Question Title: " << question.title_ << '\n';
    std::cout << "Question Description: " << question.description_ << '\n';
    std::cout << "Question View Count: " << question.view_count_ << '\n';
    std::cout << "Question Vote Count: " << question.vote_count_ << '\n';
    std::cout << "Question Status: " << question.status_ << '\n';
    std::cout << "Question Closed Remarks: " << question.closed_remarks_ << '\n';
    std::cout << "Question Bounty: " << question.bounty_.reputation_ << " reputation until " << question.bounty_.expiry_date_ << '\n';
    std::cout << "Answer View Count: " << answer1.view_count_ << '\n';
    std::cout << "Answer Vote Count: " << answer1.vote_count_ << '\n';
    std::cout << "Answer Accepted: " << (answer1.accepted_ ? "Yes" : "No") << '\n';
    std::cout << "Comment View Count: " << comment1.view_count_ << '\n';
    std::cout << "Comment Vote Count: " << comment1.vote_count_ << '\n';
    std::cout << "Tag Name: " << tag1.name_ << '\n';
    std::cout << "Tag Description: " << tag1.description_ << '\n';
    std::cout << "Tag Daily Frequency: " << tag1.daily_frequency_ << '\n';
    std::cout << "Tag Weekly Frequency: " << tag1.weekly_frequency_ << '\n';
    std::cout << "Badge Name: " << badge1.name_ << '\n';
    std::cout << "Badge Description: " << badge1.description_ << '\n';

    return 0;
}
 

You can also try this code with Online C++ Compiler

Run Code

Output

Suraj is asking a question.
Suraj earned 100 reputation.
Notification sent to Suraj.
Badge assigned to Suraj with 200 reputation.
Question Title: What is Stack Overflow?
Question Description: Can someone explain what Stack Overflow is?
Question View Count: 50
Question Vote Count: 20
Question Status: closed
Question Closed Remarks: Duplicate
Question Bounty: 100 reputation until 2023-02-01
Answer View Count: 30
Answer Vote Count: 15
Answer Accepted: Yes
Comment View Count: 10
Comment Vote Count: 5
Tag Name: programming
Tag Description: Questions related to programming
Tag Daily Frequency: 100
Tag Weekly Frequency: 500
Badge Name: Best Answer
Badge Description: Awarded to the best answer of a question

Data Structures Used

In the code, various data structures are used:

• enum is used to define named constants (e.g., account types)
• vector is used to store collections of objects (e.g., comments, photos, tags, badges)
• string stores sequences of characters (e.g., names, descriptions, text)
• int stores integers (e.g., view count, vote count, reputation)
• bool stores boolean values (e.g., accepted)
• classes define user-defined data types to model entities (e.g., Account, Notification, Badge, etc.).

Frequently Asked Questions

What is sharding?

Sharding is a database partitioning technique where a large database is horizontally split into smaller, more manageable parts called shards. Each shard is a separate instance of the database that contains a subset of the data and is stored on a separate physical server.

What is caching?

Caching is a technique in system design where frequently-used data is temporarily stored in a cache so that it can be quickly retrieved the next time the same data is needed. This can improve the performance and responsiveness of a system by reducing the time it takes to access the data, as the cache can provide the data much faster than a remote data source.

What is CDN?

CDN stands for Content Delivery Network. It is a distributed network of servers that work together to deliver web content to users based on their geographic location. The goal of a CDN is to reduce latency, improve accessibility and increase content available to users.

Conclusion

In conclusion, Stack Overflow is a valuable resource for developers, with a vast community of users that offer help and support for programming-related questions. 

The low-level design of the website involves a complex system of functional and non-functional requirements, including account creation, searching, asking questions, assigning badges, and more. 

The code uses various data structures such as enums, vectors, strings, ints, bools, and classes to store and manipulate data efficiently to achieve these requirements. 

Overall, the design of the Stack Overflow website is well-planned and optimized to provide a seamless user experience to the millions of developers who use it every day.

With this understanding, one can confidently approach complex system design problems in a product-based environment.

You can also consider our System Design Course to give your career an edge over others.

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