Mongoose - $in doesn't respect order

I think you can do it in one aggregation query. Also an input and output example will be helpful.

By the way, for your queries I think you want:

1. Get all territories near to a position
2. Return only the _id and name
3. Search clinics which territory field is the same as the _id from territories.

So I think this can be accomplished in one query like this:

db.territories.aggregate([
  {
    $geoNear: {
      near: {
        type: "Point",
        coordinates: [location.lat, location.long]
      },
      distanceField: "dist.calculated"
    }
  },
  {
    $project: {
      name: 1
    }
  },
  {
    $lookup: {
      from: "clinics",
      localField: "_id",
      foreignField: "territory",
      as: "clinics"
    }
  },
  {
    $unwind: "$clinics" // optional; it depends the output you want
  }
])

And the result is something like:

{
   "_id":2,
   "name":"territory name 2",
   "clinics":{
      "_id":ObjectId("61ea8a20f90aaa6f3e23efac"),
      "territory":2,
      "name":"clinic2"
   }
}{
   "_id":1,
   "name":"territory name 1",
   "clinics":{
      "_id":ObjectId("61ea8a20f90aaa6f3e23efab"),
      "territory":1,
      "name":"clinic1"
   }
}{
   "_id":3,
   "name":"territory name 3",
   "clinics":{
      "_id":ObjectId("61ea8a20f90aaa6f3e23efad"),
      "territory":3,
      "name":"clinic3"
   }
}

I've used mongo $geoNear example as input data and in all executions the order is the same.