I looked in the docs but couldnt find it. looking for something like the following
let promise = new Promise(someExecutor);
let promise2 = new Promise(executor2);
Promise.all([promise,promise2]).then(someFunc);
let userQ = User.find(someId);
let postQ = Post.find(someIdforPost);
//Mongoose.Query.all([userQ, postQ])??
The mongoose find function returns a promise anyways. So you can handle this similar to the 1st example in your code.
Just use Promise.all([userQ, postQ]).then(someFunc)