How to check sessions for authenticity?

Question

Node.js

Just got into sessions.
I use express-sessions.
Here is stored sid on the client. Through the post data comes from the authorization form. Then, according to the data searched in the database, a user with such a login is searched, if he finds it, it is saved req.session.save().
But the question gnaws, if somehow there is a session substitution, then how to check. There was an idea to check whether there is such a session in the storage for each request to the site.
In my opinion a simple check if(req.session.sid)is not a good idea. It's just checking the existence of a session, but not its authenticity, and each time connecting to the database, comparing is expensive.
But the question is, maybe there are simpler and faster methods? Maybe there are some built-in mechanisms?