Reproduce _.isEmpty slowness

server.js

import { Meteor } from 'meteor/meteor';
import { Mongo } from 'meteor/mongo';

Widgets = new Mongo.Collection('widgets');

if (Widgets.find().count() < 1000) {
  for (let i=0; i < 1000; i++) {
    Widgets.insert({});
  }
}

let handles = [];
for (let i=0; i<5000; i++) {
  handles.push(Widgets.find({ i }).observe({ added(){}, changed(){}, removed(){} }));
}

import Profile from 'meteor/qualia:profile';
Profile.profileDuration('zprofile', '/Users/lucas/Downloads/zprofile.cpuprofile', 5000);

handles.forEach(handle => handle.stop());