Challenge — Blog API with MongoDB

Objective

Build a REST API for a blog platform using Express + Mongoose + TypeScript. Focus on data modeling decisions and aggregation queries.

Requirements

Data Models (30 points)

Design and implement the following schemas:

User

• name, email (unique), passwordHash, role (author/admin)
• profile: embedded object with bio, avatar
• timestamps

Post

• title, slug (unique, auto-generated from title), content, excerpt
• authorId: reference to User
• tags: array of strings
• status: draft/published
• views: counter
• timestamps

Comment

• Embed comments directly in Post documents
• Each comment: userId, text, createdAt
• Maximum 100 comments per post (validate this)

Endpoints (40 points)

GET    /posts                    — paginated list, filter by tag/status
GET    /posts/:slug              — single post + increment view count
POST   /posts                   — create (auth required)
PATCH  /posts/:id               — update (author or admin only)
DELETE /posts/:id               — soft delete (set status to 'deleted')

POST   /posts/:id/comments      — add comment (auth required)
DELETE /posts/:id/comments/:cid — delete comment (owner or admin)

GET    /stats/top-authors       — aggregation: top 5 authors by total views
GET    /stats/popular-tags      — aggregation: top 10 tags by usage count

Aggregations (30 points)

• GET /stats/top-authors — use $group, $lookup, $sort, $limit
• GET /stats/popular-tags — use $unwind on tags array, $group, $sort
• GET /posts with pagination — use $facet to return items + total count in one query

Grading

Criteria	Points
Schema design with proper types	15
Embedded vs referenced decisions justified	15
All CRUD endpoints functional	20
Pagination with $facet	10
Top authors aggregation	10
Popular tags aggregation	10
Slug auto-generation on save	10
404 / validation error handling	10
Total	100

Setup

mkdir blog-api && cd blog-api
npm init -y
npm install express mongoose zod dotenv
npm install -D typescript tsx @types/express @types/node vitest

Slug Helper

import { Schema } from 'mongoose';

function generateSlug(title: string): string {
  return title
    .toLowerCase()
    .replace(/[^a-z0-9\s-]/g, '')
    .replace(/\s+/g, '-')
    .replace(/-+/g, '-')
    .trim();
}

// In your schema:
postSchema.pre('save', function () {
  if (this.isModified('title')) {
    this.slug = generateSlug(this.title);
  }
});

Bonus

• Full-text search with MongoDB text index ($text: { $search: '...' })
• RSS feed endpoint returning XML
• Rate limiting on the comment endpoint (max 5 comments per user per hour)
• Tag autocomplete endpoint using regex queries