Step 01: Create a Role for the lambda to access AppConfig.

For this tutorial, I will assign everything to all resources, but in the real world, you will need to follow the least privileged concept.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "logs:CreateLogGroup",
            "Resource": "arn:aws:logs:us-east-1:<account-id>:*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": [
                "arn:aws:logs:us-east-1:<account-id>:log-group:/aws/lambda/test:*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": "appconfig:*",
            "Resource": "*"
        }
    ]
}

Step 02: Create a new Lambda function and assign the above Created IAM Role

Step 03: Add a new Layer to the Lambda function

Step 04: Add the following code to the Lamda function to read the config

const http = require('http');
exports.handler = async (event) => {
 
 const APP_CONFIG_PORT = 2772;
 const APP_CONFIG_NAME = 'MyCloudNativeApp';
 const APP_CONFIG_ENV = 'dev';
 const APP_CONFIG_CONFIG_PROFILE = 'CloudNativeFreeForm-AppConfigHosted';
 
 let url = `http://localhost:${APP_CONFIG_PORT}/applications/${APP_CONFIG_NAME}/environments/${APP_CONFIG_ENV}/configurations/${APP_CONFIG_CONFIG_PROFILE}`;
console.log(url); 
 const res = await new Promise((resolve, reject) => {
    http.get(
      url,
      resolve
    );
  });
  
  let configData = await new Promise((resolve, reject) => {
    let data = '';
    res.on('data', chunk => data += chunk);
    res.on('error', err => reject(err));
    res.on('end', () => resolve(data));
  });
console.log(configData);
  
  const parsedConfigData = JSON.parse(configData);
         
  const response = {
    statusCode: 200,
    body: parsedConfigData,
  };
  return response;
};

Step 05: Run the Lambda and you can see the fetched features.