Queries in Azure Cosmos DB for NoSQL with NestJS

A complete REST API example demonstrating CRUD operations and advanced query capabilities using NestJS and Azure Cosmos DB for NoSQL. Youtube Video found here

Project Overview

This application demonstrates how to:

• Build a RESTful API with NestJS framework
• Connect to Azure Cosmos DB using the official SDK
• Implement CRUD operations with TypeScript
• Perform advanced queries with pagination, filtering, and sorting
• Optimize queries for performance and cost efficiency
• Handle configuration and environment variables
• Implement proper error handling and middleware

Prerequisites

Before you begin, ensure you have the following installed:

• Node.js (v20 or later)
• pnpm (v9.7 or later) or npm v10 or later
• An active Azure subscription with a Cosmos DB account
• Azure CLI (optional, for resource management)
• Postman or similar tool for testing API endpoints

Environment Setup

1. Clone the repository:

   git clone https://github.com/kenya-data-platform-user-group/Queries-in-Azure-Cosmos-DB-for-NoSQL-with-Nest.js
   cd Nest-CosmosDB-Query

2. Install dependencies:

   pnpm install

   or

   npm install

3. Create a .env file in the root directory with the following variables:

   PORT=3000
   NODE_ENV=development
   AZURE_COSMOS_DB_ENDPOINT=<your-cosmosdb-endpoint>
   AZURE_COSMOS_DB_KEY=<your-cosmosdb-key>
   COSMOSDB_DATABASE_NAME=<your-database-name>
   

Project Dependencies

The project uses the following main dependencies:

pnpm add @nestjs/config @azure/cosmos uuid class-transformer class-validator @nestjs/mapped-types

Database Structure

The application creates two containers in your Cosmos DB:

• users - Stores user information
• blogs - Stores blog entries with nested comments

Both containers are created automatically when the application starts for the first time.

Running the Application

# development mode
pnpm run start

# watch mode (recommended for development)
pnpm run start:dev

# production mode
pnpm run start:prod

API Endpoints

Blogs Resource

Method	Endpoint	Description
GET	/blogs	Get all blogs
GET	/blogs/:id	Get a specific blog by ID
POST	/blogs	Create a new blog
PATCH	/blogs/:id	Update a specific blog by ID
DELETE	/blogs/:id	Delete a specific blog by ID
GET	/blogs/with-comments	Get all blogs with comments
POST	/blogs/many	Create multiple blogs at once
GET	/blogs/mock	Create mock blogs for testing
DELETE	/blogs/all-blogs	Remove all blogs
GET	/blogs/recent-comments	Find blogs with recent comments
GET	/blogs/most-active-author-comments	Find most active comment authors
GET	/blogs/most-active	Find most active blogs by comment count
POST	/blogs/:id/comments	Add a comment to a blog
PATCH	/blogs/:blogId/comments/:commentId	Update a comment in a blog
DELETE	/blogs/:blogId/comments/:commentId	Delete a comment from a blog
GET	/blogs/:blogId/comments/:commentId	Get a specific comment from a blog

Project Structure

src
├── app.module.ts             # Main application module
├── main.ts                   # Application entry point
├── http-exception.filter.ts  # Global exception filter
├── database/                 # Database connection module
│   ├── database.service.ts   # Azure Cosmos DB service
│   └── indexing-policies/    # Custom indexing policies
├── blogs/                    # Blogs module
│   ├── dto/                  # Data Transfer Objects
│   ├── entities/             # Entity definitions
│   ├── blogs.controller.ts   # REST API controller
│   └── blogs.service.ts      # Business logic with query implementations
└──

Development Tools

This project includes several development tools:

• ESLint : Linting with TypeScript support