Get Cognito user pool identity in Lambda function

Question

I have a Lambda function handling POST requests triggered by the API Gateway. The latter is set up to authorize via a Cognito user pool authorizer. Authorization works - i

Answer 1

Use the event.requestContext.authorizer.claims.sub to get user's Cognito identity sub, which is basically their ID. This assumes you're using Proxy Integration with API Gateway and Lambda.

Here's a simple example using Node; should be similar across other SDKs.

exports.handler = async (event, context, callback) => {
    let cognitoIdentity = event.requestContext.authorizer.claims.sub

    // do something with `cognitoIdentity` here

    const response = {
        statusCode: 200,
        headers: {
            "Access-Control-Allow-Origin": "*"
        },        
        body: JSON.stringify("some data for user"),
    };
    return response;
};