What is an Azure Function? — Step-by-Step Guide with a Real Example

Azure Functions is Microsoft Azure’s serverless compute the solution. This is offering you to run short amounts of code (“functions“) without any need of setting up or personally handle servers. You give the code and specify when it should run (triggers); Azure provides infrastructure, scale, and availability. This makes Functions great for event-driven tasks like as HTTP endpoints, queue processors, timers, blob processors, and more.

Below is a friendly, practical walkthrough— from concept to a real HTTP-triggered C# function you can run locally and deploy to Azure. By reading this blogs, you able to better underastand what is an azure function.

Why should you use Azure Functions? (Short, practical arguments.)

• No server management: concentrate on the code, not the infrastructure.
• Automatic scaling: Azure automatically scales instances up and down based on the load.
• Cost-effective: Many scenarios require payment per execution (consumption plan).
• Event-driven: Native triggers for HTTP, queues, blobs, timers, Service Bus, Event Grid, and other events.
• Fast to iterate: Small deployable units for micro-workflows allow for quick iteration.

Important topics (what is an azure function)

A function is a unit of code that executes when activated.

1. Trigger — event that invokes the function (HTTP, queue, blob, timer…).
2. Binding — declarative input/output connections (e.g., automatically read from a queue or write to blob storage).
3. Function App — container for one or more functions that share configuration, runtime, and deployment.
4. Plans: Plans include consumption (pay-per-execution), premium, and dedicated (app service).
5. Durable Functions: Durable Functions is an addon for orchestration and stateful serverless processes.

What we will develop (actual example)

A basic C# Azure Function that accepts a name from a query string or JSON body and produces a greeting. You’ll run it locally and then deploy to Azure.

Prerequisites

• [.NET SDK 6 or 7/8] installed (matching Functions runtime compatibility).
• [Azure Functions Core Tools] installed.
• [Azure CLI] (az) installed and logged in (az login).
• Visual Studio Code (recommended) or Visual Studio.
• (Optional) An Azure subscription (free or existing).

If you want the exact install commands for your OS, tell me your OS and I’ll list them.

Step 1 — Create the function project (local)

Open a terminal and run:

# Create a folder
mkdir MyAzureFunctionApp
cd MyAzureFunctionApp

# Initialize a new .NET Azure Functions project
func init --worker-runtime dotnet --target-framework net6.0
# Or: func init --worker-runtime dotnet (it will detect a target framework)

Add an HTTP-triggered function:

func new --name HttpGreeting --template "HTTP trigger" --authlevel "anonymous"

This creates HttpGreeting with a template function in HttpGreeting.cs.

Step 2 — Inspect the generated code

Open the project in VS Code. Example HttpGreeting.cs (trimmed and annotated):

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using System.IO;
using System.Text.Json;

public static class HttpGreeting
{
    [FunctionName("HttpGreeting")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)]
        HttpRequest req,
        ILogger log)
    {
        log.LogInformation("HttpGreeting function processed a request.");

        string name = req.Query["name"];

        if (string.IsNullOrEmpty(name))
        {
            using var reader = new StreamReader(req.Body);
            var body = await reader.ReadToEndAsync();
            if (!string.IsNullOrEmpty(body))
            {
                try
                {
                    var doc = JsonDocument.Parse(body);
                    if (doc.RootElement.TryGetProperty("name", out var nameProp))
                        name = nameProp.GetString();
                }
                catch { /* ignore parse errors for this demo */ }
            }
        }

        if (string.IsNullOrEmpty(name))
            return new BadRequestObjectResult("Please pass a name on the query string or in the request body");

        return new OkObjectResult($"Hello, {name}! Welcome to Azure Functions.");
    }
}

What happens: the function reads a name from query string or JSON body and returns a greeting.

---

Step 3 — Run locally

Start the Functions runtime:

func start

You’ll see console output and a local URL like http://localhost:7071/api/HttpGreeting.

Test with curl or your browser:

# GET
curl "http://localhost:7071/api/HttpGreeting?name=Rohit"

# POST (JSON)
curl -X POST http://localhost:7071/api/HttpGreeting -H "Content-Type: application/json" -d '{"name":"Rohit"}'

You should get a Hello, Rohit! response.

Step 4 — Prepare Azure resources

An Azure Function App requires a few Azure resources. You can create them with the Azure CLI. Replace <RG>, <LOCATION>, <STORAGE>, <APPNAME> with your values (unique app name).

# Variables
RG="myFuncResourceGroup"
LOCATION="eastus"                # pick a region near you
STORAGE="mystorageaccount12345"  # must be globally unique (lowercase letters/numbers)
APPNAME="myfunc-app-12345"       # unique name

# Create resource group
az group create --name $RG --location $LOCATION

# Create a storage account (required for Functions)
az storage account create --name $STORAGE --location $LOCATION --resource-group $RG --sku Standard_LRS

# Create the Function App (Consumption plan, .NET)
az functionapp create \
  --resource-group $RG \
  --consumption-plan-location $LOCATION \
  --name $APPNAME \
  --storage-account $STORAGE \
  --runtime dotnet \
  --functions-version 4

This sets up a Function App you can deploy to.

---

Step 5 — Deploy from local to Azure

You can deploy using the Functions Core Tools:

func azure functionapp publish $APPNAME

Or use Visual Studio / VS Code integration to publish (GUI). After publish, your function will be available at:

https://<APPNAME>.azurewebsites.net/api/HttpGreeting

Try in browser or curl:

curl "https://<APPNAME>.azurewebsites.net/api/HttpGreeting?name=Rohit"

---

Step 6 — Test, monitor, and logs

• In the Azure Portal, first open your Function App and go to Functions and select HttpGreeting. after selecting HttpGreeting, you able to write Code and finally Test to try inputs.
• Under Monitoring you can turn on Application Insights to see telemetry (exceptions, requests, durations).
• Logs streamed from the portal or func azure functionapp logstream <APPNAME> help diagnose issues.

---

Step 7 — Make it production-ready (practical tweaks)

• Authentication & Authorization: If the endpoint should not be public, enable App Service Authentication (Azure AD, social providers) or use function keys.
• Configuration: To authenticate resources, utilize Managed Identity or save secrets and connection strings in Application Settings (Azure Portal).
• Durable Functions (orchestrator + activities) are recommended for long-running stateful sequences or orchestrations.
• Connect Application Insights to monitor stats and receive notifications.
• Connecting Deployment Center to GitHub Actions or Azure DevOps makes it possible you to automate deployments.

Configuring Your Azure Function

When you are working with Azure Functions, then proper configuration is essential for keeping your project more secure, scalable, and easy to maintain. Let’s describe each process step by step how can you achieve this.

1. Managed identities provide safe authentication –
   • Instead of hardcoding secrets or storing sensitive credentials, use Managed Identity to securely connect your Azure Function to other Azure resources such as Key Vault, Storage, or SQL Database, eliminating the need to manually maintain keys.
   • If your Managed Identity is not available, you can still secure your connection strings and secrets by storing them in the Application Settings of Azure Portal.
2. Managing Long-Running Workflows Using Reliable Functions –
   • You can consider effective azure functions if your application requires the management of complex or long-running workflows operation (for example, order processing or report generation).
   • They allow you to define an control function that handles many activity functions, which guaranteeing that your all type of process runs smoothly and faster.
   • It can be resumed if interrupted – all without incurring additional infrastructure costs.
3. Stay on Top of Your Performance with Application Insights –
   • Monitoring your apps is important as well as coding. By monitoring, you can easily tracks any bugs or performanse related operation.
   • By integrating Application Insights feature with your apps, you can easily track real-time performance metrics, detect issues early, and set up alerts for failures or unusual type of activity.
   • It’s your built-in health dashboard for everything related to your azure function app is doing.
4. Simplify your Deployments with DevOps or Github Integration –
   • Automate your deployments instead of doing them manually! With the help of Deployment Center in Azure, you can easily connect your Function App to Azure DevOps or GitHub Actions.
   • once Every time you push code changes, your updated function gets deployed automatically. This helps maintain continuous integration and delivery (CI/CD) with zero downtime.

What Kind of Work Can Azure Functions Do?

Azure Functions are like your cloud-based helpers — small and powerful pieces of code that automatically run when something happens. It is best for automating tasks, handling events, and connecting different type of services together without worrying about servers. Here are some common ways you can follow and use them:

1. Respond to webhooks and build APIs –
   • Azure Functions can be used to develop lightweight HTTP based APIs and respond to webhook events.
   • For example, when a user fills out a form or an app triggers an event, your function can handle the request immediately – no entire web server required!
2. Process messages from queues and the service bus –
   • Azure Functions work seamlessly with Azure Queue Storage and Service Bus.
   • Assume you have a large number of background tasks, such as processing orders or sending alerts; your function will automatically pick up each message and handle it in the background, making your app faster and more efficient.
3. React to File Uploads in Blob Storage –
   • When a new file (like an image or document) is uploaded to Azure Blob Storage, your azure function can kick in automatically.
   • You may also use Azure functions to perform related to files such as resize images, extract metadata, and generate image thumbnails without requiring manual interaction.
4. Run Scheduled Jobs –
   • Azure Functions can also work as a smart scheduler job using Timer Triggers.
   • You can also set them to run jobs at specific times according to your needs — like nightly database cleanup, log archiving, or sending daily reports — just like a cloud-based version of a “cron job.”

Common use cases

• HTTP APIs and webhooks (for example).
• Processing messages from queues or the Service Bus.
• Responding to blob storage uploads (image resizing and metadata extraction).
• Scheduled jobs (timer-triggered), such as evening cleanup.
• Event Grid enables event-driven pipelines.

Pricing and Hosting Options (short)

• Consumption plan: Pay per execution and resource consumed – ideal for variable workloads and little overhead.
• Premium plan: Keeps instances warm to reduce latency and supports VNET/long-running executions.
• App Service plan: Run functions on dedicated virtual machines (when you require fixed VM resources or wish to consolidate).

Best practices

• Keep functions minimal and with a single point of responsibility.
• Bindings can help you avoid boilerplate resource code.
• Avoid long-running synchronous blocking; instead, use Durable Functions for stateful orchestration.
• Secure secrets with Key Vault and Managed Identity.
• Add retries and idempotency for triggers like queues.
• Structured logging allows for better querying in Application Insights.

Short FAQ

Question: Is Azure Functions equivalent to Azure App Service?
Answer: No, Azure function and Azure App service both are totally difference to each other. App Service is a platform for deploying web apps, whereas Functions are serverless and event-driven. Functions could be working on the App Service platform (App Service plan), but the programming model and billing are separate from each other.

Question: When should I utilize Durable Functions?
Answer: Durable Functions are useful when you need to coordinate several functions in a workflow, handle long-running processes, or manage retries and stateful orchestrations.

Question: Is cold start a problem?
Answer: Cold starts (delays when an instance is launched on demand) may occur on the Consumption plan. Premium plans and pre-warmed instances decrease cold start latency.

Wrap-up (what you learned)

• An Azure Function is a small serverless unit of code that is triggered by events.
• How to make one: Build a C# HTTP function locally.
• How to run locally: I used func start and tested it with curl.
• To deploy, use az to build Azure resources and then use func azure functionapp publish to publish them.
• Production operational guidelines include monitoring, security, and scalability considerations.