Hi @shy.aberman
Welcome to the Auth0 Community!
I’m sorry for the late response. To validate session from the back-channel, our recommended way is to use the GET /api/v2/sessions/{sessionId} Manage User Sessions with Auth0 Management API.
Alternatively, you might find our OIDC Back-Channel Logout feature interesting since it allows your backend to subscribe to logout events. → OIDC Back-Channel Logout
Thanks
Dawid