Difference between cognitoIdentityId and cognito's sub

Which Category is your question related to? Auth What AWS Services are you utilizing? Cognito + Amplify Provide additional details e.g. code snippets

I have an authenticated user that when hitting an authenticated API, the APIGatewayEvent request identity object in the lambda function looks like the following:

APIGatewayEventRequestContext.identity: {
    accessKey: string;
    accountId: string;
    apiKey: string;
    caller: string;
    cognitoAuthenticationProvider: string;
    cognitoAuthenticationType: string;
    cognitoIdentityId: string;
    cognitoIdentityPoolId: string;
    sourceIp: string;
    user: string;
    userAgent: string;
    userArn: string;
}

In most tutorials I’ve seen people use the cognitoIdentityId as a primary key in their Dynamo DB table. This cognitoIdentityId looks along the lines of us-east-1:9383883-7c06-4e84-8637-01b966cd2323.

This looks very different than sub that’s found on cognito, which looks more like d014f2323-f1e8-4694-9d97-c223232. I’m leaning towards using sub as the primary key, however, it makes me feel a little uneasy that given the above event request identity object, the only way to retreive sub is by parsing the cognitoAuthenticationProvider key:

i.e. event.requestContext.identity.cognitoAuthenticationProvider.split(“:”)[2] // => returns sub

I guess my questions are:

1. Why is sub so hard to get in this object? Is it safe to do so?
2. What’s the purpose of cognitoIdentityId? Is it meant to be used as a public id?
3. Is it okay to use cognito’s sub as a primary key for a dynamo db table?

Thank you in advance

[shan4993]

Hello, there must be more implications to using one over the other. Which value, sub or identity id, should be used as a unique identifier for a user in say a dynamo table.

For instance, if a Facebook or google login api was offered in a client app along with custom login in option how would these impact sub and identity id values.

[jan-wilhelm]

Are there updates on this? @shan4993 's question is crucial to some applications!