assignment.md

Assignment: CRUD API

Description

Your task is to implement a simple CRUD API for a Product Catalog using an in-memory database underneath. Use Fastify as the framework.

Technical requirements

• Task can be implemented in JavaScript or TypeScript
• Use Fastify as the web framework
• Only fastify, @fastify/* plugins, nodemon, dotenv, cross-env, typescript, ts-node, ts-node-dev, tsx, zod and zod-related linter and its plugins, bundler and its plugins and loaders, formatter and its plugins, uuid, @types/* as well as libraries used for testing are allowed
• Use 24.x.x version (24.10.0 or upper) of Node.js
• Prefer asynchronous API whenever possible

Implementation details

1. Implemented endpoint api/products:

   • GET api/products is used to get all products
     • Server should answer with status code 200 and all product records
   • GET api/products/{productId}
     • Server should answer with status code 200 and the record with id === productId if it exists
     • Server should answer with status code 400 and corresponding message if productId is invalid (not uuid)
     • Server should answer with status code 404 and corresponding message if record with id === productId doesn't exist
   • POST api/products is used to create a record about a new product and store it in the database
     • Server should answer with status code 201 and newly created record
     • Server should answer with status code 400 and corresponding message if request body does not contain required fields or if price is not a positive number
   • PUT api/products/{productId} is used to update an existing product
     • Server should answer with status code 200 and the updated record
     • Server should answer with status code 400 and corresponding message if productId is invalid (not uuid)
     • Server should answer with status code 404 and corresponding message if record with id === productId doesn't exist
   • DELETE api/products/{productId} is used to delete an existing product from the database
     • Server should answer with status code 204 if the record is found and deleted
     • Server should answer with status code 400 and corresponding message if productId is invalid (not uuid)
     • Server should answer with status code 404 and corresponding message if record with id === productId doesn't exist

2. Products are stored as objects that have the following properties:

   • id — unique identifier (string, uuid) generated on the server side
   • name — product name (string, required)
   • description — product description (string, required)
   • price — product price (number, required, must be > 0)
   • category — product category (string, required, e.g. "electronics", "books", "clothing")
   • inStock — whether the product is in stock (boolean, required)

3. Requests to non-existing endpoints (e.g. /some-non/existing/resource) should be handled (server should answer with status code 404 and corresponding human-friendly message)

4. Errors on the server side that occur during the processing of a request should be handled and processed correctly (server should answer with status code 500 and corresponding human-friendly message)

5. Value of port on which the application is running should be stored in .env file

• Important: The .env file itself should not be committed to the repository as it is considered a security bad practice. Please consider adding the .env file to .gitignore.

  • Instead, create and commit an .env.example file that contains a list of required environment variables with reasonable default values

  • Example of .env.example contents:

    PORT=4000
    

6. There should be 2 modes of running the application (development and production):

   • The application is run in development mode using nodemon or ts-node-dev or tsx (there is an npm script start:dev)
   • The application is run in production mode (there is an npm script start:prod that starts the build process and then runs the bundled file)

7. There could be some tests for the API (not less than 3 scenarios). Example of a test scenario:

   1. Get all records with a GET api/products request (an empty array is expected)
   2. A new object is created by a POST api/products request (a response containing the newly created record is expected)
   3. With a GET api/products/{productId} request, we try to get the created record by its id (the created record is expected)
   4. We try to update the created record with a PUT api/products/{productId} request (a response is expected containing an updated object with the same id)
   5. With a DELETE api/products/{productId} request, we delete the created object by id (confirmation of successful deletion is expected)
   6. With a GET api/products/{productId} request, we are trying to get the deleted object by id (expected answer is that there is no such object)

8. There could be implemented horizontal scaling for the application. There should be an npm script start:multi that starts multiple instances of your application using the Node.js Cluster API (equal to the number of available parallelism - 1 on the host machine, each listening on port PORT + n) with a load balancer that distributes requests across them (using Round-robin algorithm). For example: available parallelism is 4, PORT is 4000. On run npm run start:multi it works the following way:

• On localhost:4000/api the load balancer is listening for requests
• On localhost:4001/api, localhost:4002/api, localhost:4003/api workers are listening for requests from the load balancer
• When user sends a request to localhost:4000/api, the load balancer sends this request to localhost:4001/api, the next user request is sent to localhost:4002/api and so on
• After sending a request to localhost:4003/api, the load balancer starts from the first worker again (sends request to localhost:4001/api)
• State of the db should be consistent between different workers, for example:
  1. First POST request addressed to localhost:4001/api creates a product
  2. Second GET request addressed to localhost:4002/api should return the created product
  3. Third DELETE request addressed to localhost:4003/api deletes the created product
  4. Fourth GET request addressed to localhost:4001/api should return 404 status code for the created product

Hints

• To generate all entities ids use Node.js randomUUID