Written by Nelson Koning
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Serverless 101: Deploying your first AWS Lambda with a Function URL

If you want to get a tiny web endpoint running without wiring API Gateway, load balancers, or extra infra, AWS Lambda Function URLs are a simple, modern way to expose a Lambda as an HTTPS endpoint. This short guide walks you through the idea, a minimal SAM-based project, and the security choices to be careful about — so you can deploy a working function quickly and safely. (docs.aws.amazon.com)

What is a Lambda Function URL — and why use it?

A Function URL is a dedicated HTTPS endpoint automatically created for a single Lambda function. It’s ideal for small HTTP handlers, webhooks, or quick proofs-of-concept where full API Gateway features are overkill. Unlike API Gateway, a Function URL points directly at one function and keeps the setup minimal. (docs.aws.amazon.com)

When you’re learning serverless, Function URLs let you focus on the code and basic cloud concepts (IAM, packaging, deployment) without adding an extra service layer. Later, if you need advanced routing, usage plans, or WAF integration, you can migrate to API Gateway. (docs.aws.amazon.com)

What you’ll need

Quick plan

  1. Initialize a SAM “hello world” app.
  2. Add a FunctionUrlConfig to the function in the SAM template.
  3. Build and deploy with SAM.
  4. Test the HTTPS endpoint.

Minimal example — files you’ll create

Below is the essentials. The SAM template uses the FunctionUrlConfig property to create the Function URL alongside the Lambda.

template.yaml (SAM)

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Hello Lambda Function URL example

Resources:
  HelloFunction:
    Type: AWS::Serverless::Function
    Properties:
      Runtime: nodejs22.x
      Handler: index.handler
      CodeUri: hello/
      MemorySize: 128
      Timeout: 10
      FunctionUrlConfig:
        AuthType: NONE       # see security notes below
        Cors:
          AllowOrigins:
            - '*'

Outputs:
  HelloFunctionUrlEndpoint:
    Description: "Function URL endpoint"
    Value: !GetAtt HelloFunctionUrl.FunctionUrl

This creates a function and a Function URL that uses the $LATEST version by default. You can also target an alias/qualified version or set AuthType to AWS_IAM for authenticated calls. The FunctionUrlConfig property is supported directly in SAM templates. (docs.aws.amazon.com)

hello/index.js (simple handler)

exports.handler = async (event) => {
  return {
    statusCode: 200,
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ message: 'Hello from Lambda Function URL!' })
  };
};

Build and deploy (SAM commands)

From the project root:

Example quick commands:

sam init --app-template hello-world --runtime nodejs22.x --name hello-furl
# edit template.yaml + hello/index.js
sam build
sam deploy --guided

Testing the endpoint

If you used AuthType: NONE, the URL is publicly reachable: curl https://.lambda-url..on.aws If AuthType: AWS_IAM, you must sign requests with SigV4 or use an IAM-authenticated tool (Postman supports SigV4); the docs explain required permissions (`lambda:InvokeFunctionUrl` + `lambda:InvokeFunction`) and how the resource policy and AuthType work together. Note: as of October 2025 new function URLs require both lambda:InvokeFunctionUrl and lambda:InvokeFunction permissions for invocation. ([docs.aws.amazon.com](https://docs.aws.amazon.com/lambda/latest/dg/urls-invocation.html?utm_source=openai))

Security and production maturity

A few practical cautions before you go live:

When to choose Function URL vs API Gateway

Final tips

If you want, I can:

Which would help you get this running fastest?