使用Firebase，React和服务器端渲染

I'm building a project with react and firebase, with an node express server. What's the best way to handle routes that need to retrieve the auth status of the user? If I understand correctly firebase doesn't store its auth data in a cookie, so I'm not sure I'll be able to know the logged in user or even if a user is logged in at all, when on the server.I'm building a project with react and firebase,