Real-Time Vocabulary Quiz

Requirement

The real-time quiz feature for an English learning application. This feature will allow users to answer questions in real-time, compete with others, and see their scores updated live on a leaderboard.

Technologies

• Node.js, Nest.js, Bull Queue, Socket.io, TypeORM
• React.js, Next.js, React-Query, Tailwind Css
• MySQL
• Redis

The Quiz-Service Architecture

The Core and the Interface

The Core

• The Core is responsible for all the business logic within the system. It encapsulates the core functionality and domain-specific rules.
• We draw inspiration from the concept of Bounded Contexts in Domain-Driven Design (DDD). Each context represents a dedicated module that groups related business logic.
• For instance, consider the following contexts in our project:
  • Quiz Context: Manages quiz sessions and user answers
  • Score Context: Evaluate user answers, calculates and updates user scores.
• The Core exposes functions that the Interface can use to serve external client requests.
• Crucially, the Core focuses solely on business logic and remains agnostic about how clients access our system (whether through REST, MVC, GraphQL, etc.). This responsibility lies with the Interface.
• In the project structure, you can find the core at: src/core

The Interface

• The Interface is responsible for exposing system functionalities to external clients.
• When a request arrives, the Interface receives it along with input data. It then converts this input into a well-typed structure required by the Core.
• The Interface performs two critical tasks:
  1. Validation: Ensures that input adheres to expected type and format.
  2. Normalization: Converts possibly weakly-typed input into a consistent type.
• Note that this normalization is distinct from business validation, which remains the Core’s responsibility.
• In the project structure, you can find the interface at: src/api

Engineers benefit from understanding the distinct roles of each part. When exploring system behavior, developers can delve directly into the Core, ignoring routing specifics, decoding/encoding intricacies, and HTTP error codes.

Conversely, making changes to the Interface—such as supporting a new protocol (e.g., adding GraphQL alongside an existing REST API)—requires no knowledge of the Core’s internals.

By maintaining this clear separation, we ensure high code quality and facilitate efficient development. 🚀

Up & Running

Prerequisite:

• MySQL installation (https://dev.mysql.com/doc/mysql-installation-excerpt/8.0/en/installing.html)
• Node.js 18.20.4 or later.
• Redis (https://redis.io/docs/latest/operate/oss_and_stack/install/install-redis/)

Run Quiz-Service:

1. Install dependencies

$ yarn install

2. Update .env file

cp .env.example .env

Update the value in .env

3. Create Database

yarn db:create

4. Run seed data

yarn db:seed

5. Run the service

yarn run:dev

Run Real-Time-Communication-Service:

1. Install dependencies

$ yarn install

2. Update .env file

cp .env.example .env

Update the value in .env

3. Run the service

yarn run:dev

Run The Quiz-Web:

1. Install dependencies

$ yarn install

2. Update .env file

cp .env.example .env.local

Update the value in .env.local

3. Run the web

yarn dev

Now you can visit http://localhost:3000/quizzes/1 from your browser.