event.requestContext.identity.cognitoIdentityId contains region AND ID

Hello,

I’m surprised to see that “event.requestContext.identity.cognitoIdentityId” presents both region & ID in the following form:
“region:ID” => “ap-southeast-1:c077febf-ff6f-48a9-99ac-2b632c5dfaac8” for example.

Any info on this ? any documentation (i haven’t been able to find this online). Is it normal ?

Thanks