Tech Task: E-Commerce simple Backend services

We're building an E-Commerce Backend backend services. Follow the instructions below to get started with your project and then carry out the tasks asked for further down.

Setup

1. Clone this repository:

git clone <repository-url>

2. cd to cloned repository

3. install packages by running

npm install

VS code setup

To provide you with a simple way to test your API endpoints locally, you can use the following extension:

REST Client for Visual Studio Code

Usage

We have provided a basic file that have the API definitions of the provided endpoints. To use it do the following:

1. Open the requests.http file in the root of the app.
2. Click the Send request link next to each request to invoke a request to that specific endpoint.
3. View the result in the sidepanel.

You can use this simple API client to test your own endpoints, or use an alternative software (such as Postman) if you prefer.

Backend

To run the backend application execute:

npm run start

Application is served on http://localhost:3000 and is a nestjs application connected to sqlite database and contain these basic APIs:

• POST request to add order/user/product
• DELETE request to remove order/user/product
• GET request to get all orders/products

Request examples could be found in file requests.http

Backend task:

While this API gives us the basic abilities to create, fetch, and delete items, it's far from sufficient for our app.

We want you to carry out the following tasks:

1. Uncomment address endpoints and fix build errors

• go to file src/app/app.module.ts and uncomment code on lines 8, 12, 19, 25
• try to fix bugs appeared in app (note: there is 3 errors, appeared next after fixing previous)

2. Implement functionality to place orders for registered user

• on POST http://localhost:3000/orders/add instead of passing userId as a body parameter fetch user from UserService read userId and add to order

3. Implement functionality to calculate totalAmount value

• on POST http://localhost:3000/orders/add fetch products from Product repository, and instead of passing totalAmount as body paramter calculate product prices and sum them up

4. Implement functionality to fetch orders only placed by current user filtered by userId added automatically

• on GET http://localhost:3000/orders fetch userId from UserService and filter orders by user

Database Query Optimization Task

Setup Instructions

1. To provide you with a simple way to view the database, you can use the following extension: SQLite Viwer
2. Execute node index.js to run the suboptimal query against the SQLite database.
3. Optimize the provided SQL query in the index.js file and explain your solution.

Task

Your task is to optimize the SQL query provided in index.js to improve performance then run node index.js to see the result.

• Consider techniques like indexing, query refactoring, or aggregation (Apply database change via index.js or directly in the database)
• Provide a brief explanation of the optimizations you applied.

Hint: Use command sqlite3 ecommerce.db to open and connect to the ecommerce.db database.

Evaluation Criteria

• Effectiveness of the optimizations.
• Clarity in explaining the rationale behind the chosen methods.
• Understanding of SQL and database performance considerations.

Best of luck!