risevest / senior-backend-test

Senior Backend Engineer Test

Develop a RESTful API using Node.js, Express, TypeScript, and an SQL database (preferrably PostgreSQL).

1. Database Design & Setup:

• Design a database with three tables: Users, Posts, and Comments. Users can have multiple posts, and each post can have multiple comments.
• Implement necessary indexing for anticipated query performance.

2. API Development:

• Endpoints to:
  • Create and retrieve users (/users).
  • Create a post for a user and retrieve all posts of a user (/users/:id/posts).
  • Add a comment to a post (/posts/:postId/comments).
  • Performance Challenge: Fetch the top 3 users with the most posts and, for each of those users, the latest comment they made. This should be achieved with efficient querying.

3. Query Optimization Task:

• Optimize the following SQL query related to the designed schema:

  SELECT users.id, users.name, posts.title, comments.content
  FROM users
  LEFT JOIN posts ON users.id = posts.userId
  LEFT JOIN comments ON posts.id = comments.postId
  WHERE comments.createdAt = (SELECT MAX(createdAt) FROM comments WHERE postId = posts.id)
  ORDER BY (SELECT COUNT(posts.id) FROM posts WHERE posts.userId = users.id) DESC
  LIMIT 3;
  

The query attempts to fetch the top 3 users with the most posts and, for each of those users, the latest comment they made. However, it's inefficient and needs optimization.

4. Middleware & Error Handling:

• Implement a simple token-based authentication middleware.
• Add basic validation for input data.
• Implement error handling for the main API routes.

Evaluation Criteria:

• Database Design: Structure, relationships, and indexing strategy.
• API Design & Implementation: RESTful practices, efficiency of the code, and especially the performance of the "Performance Challenge" endpoint.
• Query Efficacy: Ability to optimize the provided SQL query.
• Code Quality: Readability, maintainability, and use of TypeScript features.
• Error Handling: How robust the application is against unexpected situations or invalid input.

Tools/Stack

• NodeJs (TypeScript & Express)
• Postgres for pure data
• Redis
• Docker
• Postman

Tests

Unit tests are a must, submissions without tests will be ignored.

Time Duration

3 days

Submission

1. Your API endpoints should be well documented in POSTMAN.
2. Code should be hosted on a git repository, Github preferably.
3. The API should be hosted on a live server (e.g. https://heroku.com)
4. Your app should be containerized using docker.
5. Share with us through email the:
   • Repository
   • Hosted API URL
   • Postman Collection Public URL