Microservices can redirect users to the IAM system for authentication, receive an encrypted SSO token, and then use it to log in users on subsequent attempts.

 Microservices can also use the IAM system for authorization, and the SSO token can specify which resources the user is permitted to access.

https://frontegg.com/blog/authentication-in-microservices#:~:text=Microservices%20can%20redirect%20users%20to,user%20is%20permitted%20to%20access.