Azure Cosmos DB: Build a Flask app with the MongoDB API

Azure Cosmos DB is Microsoft’s globally distributed multi-model database service. You can quickly create and query document, key/value, and graph databases, all of which benefit from the global distribution and horizontal scale capabilities at the core of Azure Cosmos DB.

This quick start guide, uses the following Flask example and demonstrates how to build a simple To-Do Flask app with the Azure Cosmos DB Emulator instead of MongoDB.


  • Download the Azure Cosmos DB Emulator. The emulator is currently only supported on Windows. The sample shows how to use the sample with a production key from Azure, which can be done on any platform.

  • If you don’t already have Visual Studio Code installed, you can quickly install VS Code for your platform (Windows, Mac, Linux).

  • Be sure to add Python Language support by installing one of the popular Python extensions.

    1. Select an extension.
    2. Install the extension by typing ext install into the Command Palette Ctrl+Shift+P.

      The examples in this document use Don Jayamanne's popular and full featured Python Extension.

Clone the sample application

Now let's clone a Flask-MongoDB API app from github, set the connection string, and run it. You see how easy it is to work with data programmatically.

  1. Open a git terminal window, such as git bash, and cd to a working directory.
  2. Run the following command to clone the sample repository.

    git clone
  3. Run the following command to install the python modules.

    pip install -r .\requirements.txt
  4. Open the folder in Visual Studio Code.

Review the code

Let's take a quick review of what's happening in the app. Open the file under the root directory and you find that these lines of code create the Azure Cosmos DB connection. The following code uses the connection string for the local Azure Cosmos DB Emulator. The password needs to be split up as seen below to accommodate for the forward slashes that cannot be parsed otherwise.

  • Initialize the MongoDB client, retrieve the database, and authenticate.

    client = MongoClient("mongodb://") #host uri
    db = client.test    #Select the database
    db.authenticate(name="localhost",password='C2y6yDjf5' + r'/R' + '+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw' + r'/Jw==')
  • Retrieve the collection or create it if it does not already exist.

    todos = db.todo #Select the collection
  • Create the app

    app = Flask(__name__)
    title = "TODO with Flask"
    heading = "ToDo Reminder"

Run the web app

  1. Make sure the Azure Cosmos DB Emulator is running.

  2. Open a terminal window and cd to the directory that the app is saved in.

  3. Then set the environment variable for the Flask app with set or export if you are using a Mac.

  4. Run the app with flask run and browse to

  5. Add and remove tasks and see them added and changed in the collection.

Create a database account

  1. In a new window, sign in to the Azure portal.
  2. In the left menu, click Create a resource, click Databases, and then under Azure Cosmos DB, click Create.

    Screen shot of the Azure portal, highlighting More Services, and Azure Cosmos DB

  3. In the New account pane, specify the desired configuration for the Azure Cosmos DB account.

    With Azure Cosmos DB, you can choose one of four programming models: Gremlin (graph), MongoDB, SQL, and Table (key-value).

    In this quick start we'll be programming against the MongoDB API so you'll choose MongoDB as you fill out the form. But if you have graph data for a social media app, document data from a catalog app, or key/value (table) data, realize that Azure Cosmos DB can provide a highly available, globally-distributed database service platform for all your mission-critical applications.

    Fill out the New account pane using the information in the table as a guide.

    Screen shot of the New Azure Cosmos DB pane

    Setting Suggested value Description
    ID Unique value A unique name you choose to identify the Azure Cosmos DB account. is appended to the ID you provide to create your URI, so use a unique but identifiable ID. The ID may contain only lowercase letters, numbers, and the '-' character, and must be between 3 and 50 characters.
    API MongoDB The API determines the type of account to create. Azure Cosmos DB provides five APIs to suits the needs of your application: SQL (document database), Gremlin (graph database), MongoDB (document database), Azure Table, and Cassandra, each which currently require a separate account.

    Select MongoDB because in this quickstart you are creating a document database that is queryable using MongoDB.

    Learn more about the MongoDB API
    Subscription Your subscription The Azure subscription that you want to use for the Azure Cosmos DB account.
    Resource Group The same value as ID The new resource group name for your account. For simplicity, you can use the same name as your ID.
    Location The region closest to your users The geographic location in which to host your Azure Cosmos DB account. Choose the location closest to your users to give them the fastest access to the data.
  4. Click Create to create the account.

  5. On the toolbar, click Notifications to monitor the deployment process.

    Deployment started notification

  6. When the deployment is complete, open the new account from the All Resources tile.

    Azure Cosmos DB account on the All Resources tile

Update your connection string

If you want to test the code against a live Azure Cosmos DB Account, go to the Azure portal to create an account and get your connection string information. Then copy it into the app.

  1. In the Azure portal, in your Azure Cosmos DB account, in the left navigation click Connection String, and then click Read-write Keys. You'll use the copy buttons on the right side of the screen to copy the Username, Password, and Host into the Dal.cs file in the next step.

  2. Open the file in the root directory.

  3. Copy your username value from the portal (using the copy button) and make it the value of the name in your file.

  4. Then copy your connection string value from the portal and make it the value of the MongoClient in your file.

  5. Finally copy your password value from the portal and make it the value of the password in your file.

You've now updated your app with all the info it needs to communicate with Azure Cosmos DB. You can run it the same way as before.

Deploy to Azure

To deploy this app, you can create a new web app in Azure and enable continuous deployment with a fork of this github repo. Follow this tutorial to set up continuous deployment with Github in Azure.

When deploying to Azure, you should remove your application keys and make sure the section below is not commented out:

    client = MongoClient(os.getenv("MONGOURL"))
    db = client.test    #Select the database

You then need to add your MONGOURL, MONGO_PASSWORD, and MONGO_USERNAME to the application settings. You can follow this tutorial to learn more about Application Settings in Azure Web Apps.

If you don't want to create a fork of this repo, you can also click the deploy to Azure button below. You should then go into Azure and set up the application settings with your Cosmos DB account info.


If you plan to store your code in Github or other source control options, please be sure to remove your connection strings from the code. They can be set with application settings for the web app instead.

Review SLAs in the Azure portal

The throughput, storage, availability, latency, and consistency of the resources in your account are monitored in the Azure portal. Let's take a quick look at these metrics.

  1. Click Metrics in the navigation menu.

    Metrics in the Azure portal

  2. Click through each of the tabs so you're aware of the metrics Azure Cosmos DB provides.

    Each chart that's associated with the Azure Cosmos DB Service Level Agreements (SLAs) provides a line that shows if any of the SLAs have been violated. Azure Cosmos DB makes monitoring your SLAs transparent with this suite of metrics.

    Azure Cosmos DB metrics suite

Clean up resources

If you're not going to continue to use this app, delete all resources created by this quickstart in the Azure portal with the following steps:

  1. From the left-hand menu in the Azure portal, click Resource groups and then click the name of the resource you created.
  2. On your resource group page, click Delete, type the name of the resource to delete in the text box, and then click Delete.

Next steps

In this quickstart, you've learned how to create an Azure Cosmos DB account and run a Flask app using the API for MongoDB.You can now import additional data to your Cosmos DB account.