Keycloak Spring Stateless Problem

I am implementing this feature because I want every backend call to verify the session against Keycloak. This is important because if a session is closed from Keycloak, it doesn’t terminate the session on my end, allowing access even when the user is no longer logged in through Keycloak. My goal is to make my project stateless, but despite numerous attempts, I have not been successful. Here is what I have tried so far:(on the images)

It keep resend me to the domain of keycloak where I have the 502 Bad Gateway error

A Vaadin Flow application is never stateless, therefore this does not make sense. If you want to ensure that users are always authenticated in keycloak, you have to check every important call against the currently valid access token which you have to refresh constantly against the keycloak server with the refresh token; once keycloak does not create new access token based on your given refresh token the session in invalid.