[SOLVED] Issue with _id generated outside Meteor?

I’m having an issue with a collection which is updated out of Meteor. Specifically I’m using Mongo’s aggregate()

Is there a reason why executing from mongo console: collection.insert({_id:“A”, val:10}) would not update Meteor server/ui reactively?

See a repo with the reproducible error here: https://github.com/keyscores/meteor-aggregation-issue

[Solved] There is no issue with _id, the issue is with mongo’s aggregate pipeline specifically using $out. Somehow it invalidates collections for Meteor. See here: