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A CRUD Operation Demo On NestJS Using Azure Cosmos DB

In this article, we are going to implement  CRUD operations into the NestJS application using Azure Cosmos DB.

Azure Cosmos DB:

Azure Cosmos DB is a fully managed NoSQL database. NoSQL says data will be stored as a key/value JSON document. Cosmos DB provides 'High Availability' and 'Low Latency' for any application. Cosmos DB is very quick in response delivering, auto-scaling, effective auto failure management, etc.

Any existing application that works on different DBs can be easily migrated to Azure CosmosDB as it provides APIs for integration like 'SQL/Core API'(most recommended API, our demo uses this 'SQL/Core API'), 'MongoDB API', 'Cassandra API', 'Germlin API', 'Table API'.

Let's understand the structure of the Cosmos DB:
  • Create an Azure Cosmos Account with an appropriate subscription inside of the Azure portal.
  • After creating the Cosmos Account, we can manage the data of our account by creating 'Database', 'Containers', and items.
  • Azure Cosmos 'Containers' means a 'Collection' or 'Table' or 'Collection' based on our APIs like 'SQL/Core API', 'MongoDB API', 'Cassandra API', etc.
  • Container contains 'Items', 'Stored Procedure', 'user-defined functions', 'triggers', etc.
  • Items inside of the Container depend on its type which means if a container is 'Table' then items will be 'Rows', if a container is 'Collection' then items will be documents, etc.
Note: Cosmos DB means NoSQL stores data as key/value. But above we discussed 'Container' that can be 'Collection', 'Table', 'Graph', etc is a representation for querying the Cosmos DB by all supported APIs.

Partition Key: -  
  • Azure Cosmos DB uses partitioning to scale individual containers in a database to meet the performance needs of our application. 
  • While partitioning, the item in a container is divided into logical partitions. 
  • Logical partitions are formed based on the value of the partition key that is associated with each item in a container.
  •  All the items in the logical partition have the same partition key value.
  • For example, the 'country' property is made as to the partition key, then items with a country name like 'India' are stored in one logical partition, and items with a country name like 'Italy' store in one logical partition, and so on.
  • So it is always advisable to use the most common and unchangeable 'property' as a partition key to get more performance and to manage the Price to spend on CosmosDB consumption.
  • If your items contain no proper property to use as a 'partition' key then we can use the 'Id' property.

Why To Use Azure Cosmos DB:

  • High Availability
  • Low Latency
  • Effect cost management pays the service on use only
  • NoSQL Database
  • Easy migration from any backend to Azure Database.
  • Auto Scale Up
  • Auto Maintenance
  • Effective Global Distribution

Create Azure Cosmos DB:

Signup with the azure portal and then log in to the Azure portal and navigate to the home page ( Then select 'Create A Resource'.

Step 2:
In the 'Create A Resource' page select 'Azure Cosmos DB'.

In 'Select API option' page choose 'Core(SQL) - Recomended'

Step 4:
In 'Create Azure Cosmos DB Account - Core(SQL)', inside of the 'Basic' tab, enter the 'Project Details
(a) Select your subscription
(b) Create a new resource group. The resource Group acts as a container or folder to our Cosmos DB.
(c) Give Account Name, based on your account name domain will be created so make sure to give a proper name.
(d) Location, select your nearest location for azure hosting, you can leave the default as a quick start.
(e) Capacity mode can choose default.
(f) App Free Tier Discount, is a very wise choice to choose by learners.
(g) Limit total account throughput can choose the default
Step 5:
Remaining tabs like 'Global Distribution', 'Networking', 'Backup Policy', 'Encryption', 'Tags' can use default values. So click on 'Review + create' button directly.

Finally, click on the 'Create' button to create an Azure Cosmos DB Account.

Step 7:
Click on the 'Go to resource' button.

Step 8:
(a) In the Azure Cosmos DB account, in left-hand side menu select 'Data Explorer'.
(b) Click on 'New Container'.
(c) In the container form let's give details
(d) Choose 'Create New'(for creating a new database in Azure Cosmos DB Account). Then specify the name of the database(database id). I will name my database as 'Vehicles'.
(e) The 'Share throughput across containers' choose default.
(f) The 'Database throughput' chooses to default i.e 'Auto Scale'.
(g) The 'Database Max RU/s' level default value. The 'Request Unit/second' calculates price.
(h) Specify the container id. For our demo let's define 'Car'. The container is like a 'Table'.
(i) The 'indexing' choose 'Auto'.
(j) The 'Partition key' value is one of the names of property of the documents we store. To this demo, my JSON document contains properties like 'id', 'make', and 'model'. I will use 'make' as my partition key for my demo.
(k) Finally click on the 'Ok' button. Then we can observe a Database like 'Vehicles', container like 'Car' get created. (Note: These database names, and container name will be used by our NestJS application)
Step 9:
Select our 'Vehicle' database then select our container 'Car', then select 'Items' then Cosmos DB window editor shows up. Then click on 'New Item', then add the sample item(document) we want to store, and then click on 'Save'.

Step 10:
Edit Filter drop-down to write SQL queries to fetch our items(document)

Step 11:
Now go to 'Key' left-hand side menu and copy the 'URL' and 'Primary Key' value we are going to use in our NestJs application.

Create A NestJS Application:

Let's create a NestJS application to accomplish our demo.
Command To Install NestJS CLI
npm i -g @nestjs/cli

Command To Create A NestJS App
nest new your_project_name

Install Required NPM Packages:

Let's install the required NPM packages.
npm install @azure/cosmos

npm i --save @nestjs/azure-database

Configure AzureCosmosDbModule:

Now let's configure AzureCosmmosDbModule into the AppModule.
import { AzureCosmosDbModule } from '@nestjs/azure-database';
import { Module } from '@nestjs/common';
// code hidden for display purpose
  imports: [
export class AppModule {}
  • Imported AzureCosmosDbModule from the '@nestjs/azure-database' library.
  • (Line: 7) Declare our Azure Cosmos DB database name to 'dbName'.
  • (Line: 8) Declare our Azure Cosmos DB URL to 'endpoint'.
  • (Line: 9) Declare our Azure Cosmos DB primary key to  'key'.

Create A New Module Like 'CarModule':

We have created a container like 'Car' in Azure Cosmos DB. So let's create a new module like 'CarModule', that deals with our 'Car' container in Azure Cosmos DB.

Let's run the below command to create the 'Car' Module
nest g mo car

Now let's create a type 'car.entitiy.ts' that represents our Azure Cosmos DB container.
nest g cl car/car.entity --flat --no-spec

Let's update our 'car.entity.ts' file as below.
import { CosmosPartitionKey } from "@nestjs/azure-database";

export class Car {
  id: string;
  make: string;
  model: string;
  • Here created our class as 'Car' name of the car must match with our Azure Cosmos DB container.
  • Here class properties like 'id', 'make', 'model' names must match with document properties of the Azure Cosmos DB container.
  • Here specific our partition key property with the help of  '@CosmosPartitionkey' attribute that loads from the '@nesjs/azure-database.'
Now configure our 'Car' entity into the 'CarModule'.
import { AzureCosmosDbModule } from '@nestjs/azure-database';
import { Module } from '@nestjs/common';
import { Car } from './car.entity';

  imports: [AzureCosmosDbModule.forFeature([{ collection: 'Car', dto: Car }])],
  controllers: [CarController],
export class CarModule {}
  • (Line: 6) Defined the 'AzureCosmosDbModule.forFeature({})'. So 'forFeature()' will be registered in child modules like 'CarModule', 'forRoot()' will be registered in parent module like 'AppModule'. Here collection means name our Azure Cosmos DB container, the 'dto' need to provide our 'Car' type.

Create A New Controller Like 'CarController':

Let's create a new controller like 'CarController', run below command.
nest g co car
import { Container } from '@azure/cosmos';
import { InjectModel } from '@nestjs/azure-database';
import { Controller } from '@nestjs/common';
import { Car } from './car.entity';

export class CarController {
  constructor(@InjectModel(Car) private readonly carContainer: Container) {}
  • Here injected the token like '@InjectModel(Car)' that loads from the '@nestjs/azure-database' and its type is 'Container' that loads from the '@azure/cosmos'.
Now let's create API a response model like 'car.dto.ts'
nest g cl car/car.dto --flat --no-spec
export interface ICarDto {
  id: string;
  make: string;
  model: string;

Read Operation:

Let's implement the read operation by fetching all the items from the Azure Cosmos DB container.
import {  Get } from '@nestjs/common';
import { ICarDto } from './car.dto';
import { Car } from './car.entity';

async getCars() {
  var sqlQuery = 'select * from c';

  var consmosResults = await this.carContainer?.items
  var fanal =<ICarDto>((value) => {
	  return {
		make: value.make,
		model: value.model,
  return fanal;
  • (Line: 7) Here we defined a simple SQL query to fetch all the data. Here 'c' can be given any other character or string inside of the query.
  • (Line: 9-11) Here invoking the Azure Cosmos DB for fetching the items based on the query we framed.
  • (Line 12-19) Response from the Azure Cosmos DB is mapped with our response type 'ICarDto' and then returns the response.

Create Operation:

Let's implement create operation to save a new item into the container of the Azure Cosmos DB.
import { Body,, Post } from '@nestjs/common';
import { ICarDto } from './car.dto';
import { Car } from './car.entity';

async create(@Body() payload: ICarDto) {
var newCar = new Car(); = '2';
newCar.make = payload.make;
newCar.model = payload.model;
var { resource } = await this.carContainer.items.create(newCar);
return {
  make: resource.make,
  model: resource.model,
  • (Line: 7-10) Mapping our user payload to the 'Car'.
  • (Line: 11) Invoking the Azure Cosmos DB to save the new item into the container.
step 1:

step 2:

Update Operation:

Let's implement the update operation to update an item in the container at Azure Cosmos DB.
import { Body, Put } from '@nestjs/common';
import { ICarDto } from './car.dto';
import { Car } from './car.entity';

async update(@Body() payload:ICarDto){
var carToUpdate = new Car(); =;
carToUpdate.make = payload.make;
carToUpdate.model = payload.model;

var {resource} = await this.carContainer.items.upsert(carToUpdate);
return {
  make: resource.make,
  model: resource.model,
  • (Line: 12) Invoking the Azure Cosmos DB to update the items inside of the container.
step 1:

step 2:

step 3:

Delete Operation:

Let's implement the delete operation to remove an item from the container of the Azure Cosmos DB.
import { Delete, Query } from '@nestjs/common';

async remove(@Query('id') id:string, @Query('partitionkey') partitionkey:string){
await this.carContainer.item(id, partitionkey).delete();
return "deleted";
  • Here to remove or delete an item depends on 'id' and 'partitonkey'(for our demo partition key value is the value of the 'make' property) values.

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Wrapping Up:

Hopefully, I think this article delivered some useful demo on consuming Azure Cosmo DB from the NestJS application. using I love to have your feedback, suggestions, and better techniques in the comment section below.

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  1. Can you please tell how we can write test case for above functionality in jest.


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