Requiremenet

https://github.com/elsa/coding-challenges/blob/main/README.md

• time to do: 3-5 days

Summary about this Challenge

Work load:

• Analyze requirement and choose a good solution: 1h
• Coding: 4h
• Write Diagram and report: 2h

Missing on Coding:

• Unit Test for application
• Refactor
• Implement the Infrastrure

Part 1: System Design

Overal Architecture : Event Streaming Microserices

Architecture Overview Diagram

Component Description:

1. On Devices: Mobile App (.Net MAUI : Android & iOS) & Web App (.Net Blazor)

2. API Gateway (.net Core 8):

   • manage (CRUD) Quiz, User, UserParticipate (UserQuiz)...
   • Data save on PosgreSQL (RMDS)
   • calculate points and trigger UserAnswers event to KSQL

3. KSQL (streaming Database) which realtime process based on event from #1 and push updates to UI

   • Save events to UserAnser topic when users submit answers of UserQuiz
   • realtime process the score calculation of UserQuiz and save event to UserQuiz topic, which update the UserQuiz Material View
   • realtime update the LeaderBoard's Material View
   • push update to UI ( Device App) about Score Update, and LeaderBoard

4. Kafka: High performance and Infinite Storage , profile topics for KSQL

   • long-life data such as : UserAnsers, UserQuiz, ...
   • and more User's Interactive: such as, click, back,...

5. Confluent Cloud: reference a Data Streaming Platform, includes KSQL, Kafka,... Apache Flink

   • Advanced solution for large-scale Streaming Appcation and Data Platform
   • run on multiple clouds and on premise
   • easy to intergrate with M/S

Data Flow:

Explain how data flows through the system from when a user joins a quiz to when the leaderboard is updated.

1. When a user join a quiz, insert or update the UserQuiz table on PostgreSQL, return userQuizId

2. When an answer of a question is submitted,

   1. insert new event with UUID and {userQuizId, questionId, answer, score}. Value of score could be calculate before submit, or after submited by a Realtime Calculation, integrated with KSQL
   2. Calculate Score by Sum of Score of UserAnswer's score of this userQuizId
   3. Insert event to UserQuizResult to topic, it will push update to MaterialViews of ScoreUpdate and LeaderQuiz (the leader board of a quiz);

3. More Flow: update Global LeaderBoard

   1. when the User completed a Quiz, calculate total Score of User, compare with other Users on LeaderBoard

Technologies and Tools:

• backend: .net 8, c#, EF, PostgreSQL
• Confluent Cloud with KSQL, Kafka,
• More with Confluent
  • Snowflake for Big Data Driven Culture
  • Apache Flink for complex - realtime processing
  • Machine Learning Plugin
  • ChatGPT plutings

Implementation

Clean Architecture & Domain Driven Design

Advantages 1.Independent of Frameworks. 2.Testable. 3.Independent of UI. 4.Independent of Database. 5.Independent of any external agency

Entities:

. QuizAggregate :

• Quiz has one-many Question
• Question has many Answer (object valu) . UserAggregate: registered User

. UserQuizAggregate: A quiz have users joined

• UserQuiz have many UserAnswers :

Interfaces (And Services)

Requirements for the Implemented Component:

• Real-time Quiz Participation: Users should be able to join a quiz session using a unique quiz ID.
• Real-time Score Updates: Users' scores should be updated in real-time as they submit answers.

public interface IUserQuizService
{
    public UserQuiz JoinQuiz(int userId, int quizId);

    public bool SubmitAnswer(UserQuiz userQuiz, Question question, Answer answers);
    public int ScoreUpdate(int userQuizId);
}

• Real-time Leaderboard: A leaderboard should display the current standings of all participants in real-time.

public interface IQuizService
{
  public IList<User> LeaderBoard(Quiz quiz); 
  public IList<User> LeaderBoard(); 
}

Build For the Future:

1. Clean Architecture :- for complex business login in future
   • Maintainability:
2. Event Streaming Microservices with Confluent Cloud is for
   • Scalability:
   • Performance:
   • Reliability:
   • Monitoring and Observability: