Create a Function App

Go to Azure Portal > Create a Resource > Compute > Function App

Basic Setup:

• Runtime stack: Python
• Region: Closest to your users
• Hosting plan: Consumption (pay-per-use)

Choose the Trigger Type: HTTP

Once the Function App is ready, go to Functions > Add

Choose HTTP trigger

Give it a name (e.g., GetUsers) and choose Authorization level: Function (or Anonymous for testing)

Write the API Code

import azure.functions as func
import json

def main(req: func.HttpRequest) -> func.HttpResponse:
    name = req.params.get('name')
    if not name:
        try:
            req_body = req.get_json()
        except ValueError:
            pass
        else:
            name = req_body.get('name')

    if name:
        return func.HttpResponse(f"Hello, {name}!")
    else:
        return func.HttpResponse("Please pass a name on the query string or in the request body", status_code=400)

Output:

GET https://.azurewebsites.net/api/GetUsers?name=Azure

Returns: Hello, Azure!

Test Your API

You can test with:

curl "https://.azurewebsites.net/api/GetUsers?name=Azure"

Or use Postman for a POST request with a JSON body.

Add More Routes

Add more function files, like:

• GetUserById
• AddUser
• DeleteUser
• UpdateUser

You now have a mini-REST API!

Persist Data

Bind Azure Functions to storage:

• Cosmos DB: Add a user, retrieve by ID
• Blob Storage: Upload or download files
• Table Storage: Lightweight key-value storage

Example: Add Cosmos DB binding in function.json

{
    "bindings": [
        {
        "type": "cosmosDB",
        "name": "outputDocument",
        "databaseName": "UsersDB",
        "collectionName": "Users",
        "createIfNotExists": true,
        "connectionStringSetting": "CosmosDBConnection",
        "direction": "out"
        }
    ]
}

Secure Your API

Use function keys or Azure AD

Add rate limits and IP restrictions in Function App settings

Monitor and Scale

Azure Functions scale automatically under load

Use Application Insights for logs, errors, and performance

View metrics under “Monitoring” in the Function App blade