Login into laravel on another website (via api)

Hi. We have two systems. One is laravel the other a SaaS solution, where user can login. We get infos via webhook like (User with ID 139 logged in). Is it possible to have session logins stored in database and login the user automatically, when he is logged in on the other side. I mean, when he comes back to us, he should be logged in. But when I see it right the session use the payload, what would mean, the only way to do it is to redirect the user directly after login with the information encrypted to our page, to login the user. Is that right. Or is there a way without doing that redirect? Thx.