AWS Cognito User Migration - Exception during user migration - amazon-cognito

Question

I have created userpool and trying to migrate user from RDS which invokes lambda function that returns the updated event object. but its not working for me.
I have followed as provided solution by removing below 2 fields, still not working .. :(
"desiredDeliveryMediums": "EMAIL",
"forceAliasCreation": "false"
Here is the response object that am sending from lambda. still facing same issue - Exception during user migration
Please let me know what am missing here. Thanks in advance
def lambda_handler(event, context):
print event
event["response"] = {
"userAttributes": {
"email": event["userName"],
"email_verified": "true",
},
"finalUserStatus": "CONFIRMED",
"messageAction": "SUPPRESS",
"desiredDeliveryMediums": "EMAIL",
"forceAliasCreation": "false"
}
print event
return event

Answer 1

I was having this problem, and I overcame it by increasing the memory allocated to the lambda from the default 128MB to 1024MB. I am using cdk to deploy, so I did this in the lamdba creation:
const nodeUserMigration = new NodejsFunction(this, 'myLambdaName', {
entry: path.join(
__dirname,
'userMigration.ts'
),
runtime: Runtime.NODEJS_18_X,
timeout: Duration.minutes(5),
memorySize: 1024, // This is what I added to overcome the `UserNotFoundException: Exception migrating user in app client (redactedClientId)`
environment: {
// redacted environment variables
},
});

Answer 2

Instead of
return event
You need
context.succeed(event)
It is probably possible to use return event directly; however, there would be other properties required to get Cognito to recognize it (things such as isBase64Encoded) and I don't know what they might be. Neither does Amazon have any documentation on them.
Oh, and desiredDeliveryMediums should be an array of strings.