Execute multiple queries at once in Mongoose
If you are expecting only one result by both of your conditions then you could use User.findOne - it will return the first found result.
User.findOne({ $or: [ { _id: req.body.userId }, { username: decodedUser.username} ]}, (err, user) => { console.log("user\n", user)})Edit
Since you said that you need to get 2 results and you want to have then in the result you can also run 2 queries in parallel and use promises to get the result. E.g.
Promise.all([ User.find({ _id: req.body.userId }), User.find({ username: decodedUser.username})]).then( ([ user, member ]) => { console.log( util.format( "user=%O member=%O", user, member ) );});