timedCatFind.js

const Cat = Mongoose.model('Cat', { name: String });
const CatProto = Object.getPrototypeOf(Cat); // this is the clean way to access an object's prototype. Please don't use __proto__ anymore.
const find = CatProto.find; // we take a reference on the orignial 'find method'
CatProto.find = function (...args) { // we replace the 'find' method on the prototype

    const res = find.apply(this, args); // we call the original method we overrided

    const exec = res.exec;
    res.exec = async function () { // exec is the method actually firing the request on mongoose.

        console.time('cat.find');
        try {
            const result = await exec.apply(this, arguments);
            console.timeEnd('cat.find');
            return result;
        }
        catch (err) {
            console.timeEnd('cat.find');
            throw err;
        }
    };
    return res;
};