How to Design Nested Documents for a Blogging App in MongoDB

Code companion for the article How to Design Nested Documents for a Blogging App in MongoDB.

Each example file maps directly to a section of the article and can be read alongside it. The repo also ships a small Express REST API that puts the final recommended schema into practice.

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Prerequisites

• Node.js 18+
• A MongoDB instance — local (mongodb://localhost:27017) or Atlas
• pnpm (or npm/yarn)

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Setup

1. Install dependencies (from the repo root):

   pnpm install

2. Configure environment variables:

   cp .env.example .env

   Edit .env and fill in your connection string:

   Variable	Default	Description
   MONGODB_URI	mongodb://localhost:27017	MongoDB connection string
   MONGODB_DB	blogging_app_examples	Database name used by examples and API
   PORT	3000	Port for the Express server

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Running the examples

All scripts are run from the repo root.

Run a single example file

node src/examples/02-embed-vs-reference.js

Replace the filename with whichever example you want to explore. Files marked as snippets below are not executable — they exist purely as annotated code for the article.

Create indexes for the final schema

Must be run before seeding or using the API:

node src/examples/10-final-schema/schema.js

Seed sample data

Populates users, posts, and comments collections so you can explore the final schema and hit the API with real data:

node src/examples/seed.js

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Running the API server

The Express app exposes a REST API backed by the final schema and includes Swagger docs.

Development (auto-restarts on file changes):

pnpm dev

Production:

pnpm start

Once running:

Endpoint	Description
GET /api/posts	List posts
GET /api/posts/:id	Get a post
POST /api/posts	Create a post
GET /api/users	List users
GET /api/users/:id	Get a user
GET /api/:postId/comments	List comments for a post
POST /api/:postId/comments	Create a comment
GET /api-docs	Swagger UI

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Example files

File	Article section	Runnable
01-entities.js	What entities exist in a blogging application?	No (snippets)
02-embed-vs-reference.js	When should you embed documents?	Yes
03-blog-post-structure.js	How should a blog post document be structured?	Yes
04-comments-embedded.js	Should comments be embedded inside blog posts?	Yes
05-comments-separate-collection.js	Unbounded comments — Option 1: separate collection	Yes
06-comments-hybrid.js	Unbounded comments — Option 2: hybrid	Yes
07-threaded-replies.js	How do nested replies affect schema design?	Yes
08-optimization.js	How do you optimize nested documents for performance?	Yes
09-common-mistakes.js	What are common mistakes with nested documents?	No (snippets)
10-final-schema/	Final recommended schema + index setup	Yes
seed.js	Sample data for the final schema	Yes