Passport.js - Error: failed to serialize user into session

If you decide not to use sessions, you could set the session to false

app.post('/login', passport.authenticate('local', {
  successRedirect: '/accessed',
  failureRedirect: '/access',
  session: false
}));

It looks like you didn't implement passport.serializeUser and passport.deserializeUser. Try adding this:

passport.serializeUser(function(user, done) {
  done(null, user);
});

passport.deserializeUser(function(user, done) {
  done(null, user);
});