Execution failed due to configuration error: Malformed Lambda proxy response

Question

Hi everyone,

I am working on a small cloud project, the goal of it is to invoke a Lambda function throughout Amazon API Gateway.

Business logic is not implemented yet but Lambda function is going to get email and password values from request body and then will persist these values in a DynamoDB table called "users"

**API endpoint:**

```
POST-> https://{API_ID}.execute-api.{REGION}.amazonaws.com/prod/user
```

**Request body:**
```
{
	"email":"test@mail.com",
	"password":"test12345"
}
```

**Lambda implementation:**

Right now as a way to validate lambda function is receiving request body correctly I am just getting email,password and then I return this values as function response

```
  const body = JSON.parse(event.body);
  
  const email = body.email;
  const password = body.password;

return  {
    statusCode: 200,
    body: {
      email,
      password,
    },
  };
```

**Lambda testing:**

Function is being invoked from API Gateway  in Manage Console

![Enter image description here](/media/postImages/original/IMOfzygtamTFSfua4fx4i-8g)

**Exception:**

When clicking on Test button I get this exception

```
Response body

{"message": "Internal server error"}

...

Response headers

{
  "x-amzn-ErrorType": "InternalServerErrorException"
}

...

Execution failed due to configuration error: Malformed Lambda proxy response
```

Error description might suggest my response is not structured properly but I am not sure about it.

**CDK Stack:**

Here are the cloud resources and configuration I am provisioning

```
    // 1. Lambda function
    const userSignUpFn = new lambda.Function(this, "userSignUpFn", {
      functionName: "user-sign-up",
      runtime: lambda.Runtime.NODEJS_18_X,
      code: lambda.Code.fromAsset(
        path.join(__dirname, "../src/lambda/user-sign-up")
      ),
      handler: "index.handler",
      architecture: lambda.Architecture.X86_64,
    });

// 2. ApiGateway
    const userApi = new apigateway.LambdaRestApi(this, "usersApi", {
      restApiName: "users-api",
      handler: userSignUpFn,
    });
    const user = userApi.root.addResource("user");
    user.addMethod("POST");

// 3. DynamoDB table
    const usersTable = new dynamodb.Table(this, "usersTable", {
      tableName: "users",
      partitionKey: { name: "email", type: dynamodb.AttributeType.STRING },
      removalPolicy: cdk.RemovalPolicy.DESTROY,
    });
```

Thanks in advance for your assistance! :)

Accepted Answer

Hi,

Take a look at the following example, it may be of help to you.

```
export const handler = function(event, context, callback) {
    const body = JSON.parse(event.body)
    const email = body.email
    const password = body.password
    var res ={
        "statusCode": 200,
        "headers": {
            "Content-Type": "*/*"
        },
        "body": JSON.stringify({email, password})
    };
    callback(null, res);
};

```

Execution failed due to configuration error: Malformed Lambda proxy response

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