Problem statement
We see that user_ids for users logging in with an external identity provider have a format as follows:
{identity type}|{optional identity provider name}|{unique user id in the provider}
What is the maximum character count that these user_ids can have?
Solution
The maximum character limit for the unique user ID is 255 characters. This limit is for the {unique user id in the provider} string, excluding identity types such as samlp, google-oauth2, and the optional identity provider name. The optional identity provider name can be up to 128 characters.