How to access dataset of an identity in cognito federated identities from lambda

Let me start with the overall description of what I'm trying to achieve. I'm building a serverless API using Lambda, Cognito (Federated Identities), API Gateway etc. I'm using aws_iam as the authorizer in API Gateway. In some endpoints, I need to access for example user e-mail or username or whatever so I can send it back in the response (also data of users who did not make the request). I guess I'm looking for some kind of "admin" access to the identity pool so I can retrieve data based on cognitoIdentityId.

Now in my case, this data is stored in a dataset in Cognito. The question is, how can I access this data from my Lambda function (node.js)? Is this a good approach at all? Should I use something else instead of datasets? Is there a working example somewhere?

I will be happy to provide more details if necessary.

Thanks

via gabo