MongoDB inconsistent aggregate call between queries - mongodb

Question

I have two tables. videos and youtubes. I want to do a $lookup on videos.youtube and match that to youtubes._id and then $match that data based on a youtubes field. Which is working fine, but there are some huge inconsistencies between queries that should be identical in nature, or at the very least close to.
Query 1: returns 8261 documents. Takes [40, 50]ms to execute
db.getCollection('videos').aggregate([
{ '$sort': { date: -1 } },
{
'$lookup': {
from: 'youtubes',
localField: 'youtube',
foreignField: '_id',
as: 'youtube'
}
},
{ '$match': { 'youtube.talent': true } },
])
Query 2: returns 760 documents. Takes [470, 500]ms to execute
db.getCollection('videos').aggregate([
{ '$sort': { date: -1 } },
{
'$lookup': {
from: 'youtubes',
localField: 'youtube',
foreignField: '_id',
as: 'youtube'
}
},
{ '$match': { 'youtube.id': 7 } },
])
Query 3: returns 760 documents. Takes [90, 100]ms to execute
db.getCollection('videos').aggregate([
// { '$sort': { date: -1 } },
{
'$lookup': {
from: 'youtubes',
localField: 'youtube',
foreignField: '_id',
as: 'youtube'
}
},
{ '$match': { 'youtube.id': 7 } },
])
All fields used in the queries are indexed. What stands out is that the $sort statement in Query 2, apparently uses roughly 400ms to execute, yet in Query 1 that uses the same $sort statement in the same location in the pipeline and it only uses [40, 50]ms.
I've used the { explain: true } option to look for differences between Query 1 and Query 2 that could explain the speed differences, but they are identical except for the $match portion.
Any solution/suggestions for bringing Query 2 up to speed with Query 1? Or at the very least an explanation for the huge differences in speed?
Another weird thing discovered while making this post
Query 4: returns 9378 documents. Takes [25, 35]ms to execute
db.getCollection('videos').aggregate([
{ '$sort': { date: -1 } },
{
'$lookup': {
from: 'youtubes',
localField: 'youtube',
foreignField: '_id',
as: 'youtube'
}
},
{ '$match': { 'youtube.clipper': true } }
])
Query 5: returns 9378 documents. Takes [600, 680]ms to execute
db.getCollection('videos').aggregate([
//{ '$sort': { date: -1 } },
{
'$lookup': {
from: 'youtubes',
localField: 'youtube',
foreignField: '_id',
as: 'youtube'
}
},
{ '$match': { 'youtube.clipper': true } }
])
At this point I'm stumped as to what is happening. Originally I thought it had to do with Number vs Boolean, but as Query 4 and Query 5 shows it clearly has 0 impact. And it seems random.
Indexes just in case (for youtubes)
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "holo-watcher.youtubes"
},
{
"v" : 2,
"unique" : true,
"key" : {
"id" : 1
},
"name" : "id_1",
"ns" : "holo-watcher.youtubes",
"background" : true
},
{
"v" : 2,
"key" : {
"name" : 1
},
"name" : "name_1",
"ns" : "holo-watcher.youtubes",
"background" : true
},
{
"v" : 2,
"unique" : true,
"key" : {
"channelId" : 1
},
"name" : "channelId_1",
"ns" : "holo-watcher.youtubes",
"background" : true
},
{
"v" : 2,
"key" : {
"clipper" : 1
},
"name" : "clipper_1",
"ns" : "holo-watcher.youtubes",
"background" : true
},
{
"v" : 2,
"key" : {
"talent" : 1
},
"name" : "talent_1",
"ns" : "holo-watcher.youtubes",
"background" : true
},
{
"v" : 2,
"key" : {
"debut" : 1
},
"name" : "debut_1",
"ns" : "holo-watcher.youtubes",
"background" : true
}
]
indexes (for videos)
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "holo-watcher.videos"
},
{
"v" : 2,
"unique" : true,
"key" : {
"videoId" : 1
},
"name" : "videoId_1",
"ns" : "holo-watcher.videos",
"background" : true
},
{
"v" : 2,
"key" : {
"title" : 1
},
"name" : "title_1",
"ns" : "holo-watcher.videos",
"background" : true
},
{
"v" : 2,
"key" : {
"date" : 1
},
"name" : "date_1",
"ns" : "holo-watcher.videos",
"background" : true
}
]
{ explain: true } output for Query 5 (nearly identical to Query 1 and Query 2):
{
"stages" : [
{
"$cursor" : {
"query" : {},
"sort" : {
"date" : -1
},
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "holo-watcher.videos",
"indexFilterSet" : false,
"parsedQuery" : {},
"winningPlan" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"date" : 1
},
"indexName" : "date_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"date" : []
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "backward",
"indexBounds" : {
"date" : [
"[MaxKey, MinKey]"
]
}
}
},
"rejectedPlans" : []
}
}
},
{
"$lookup" : {
"from" : "youtubes",
"as" : "youtube",
"localField" : "youtube",
"foreignField" : "_id"
}
},
{
"$match" : {
"youtube.clipper" : {
"$eq" : true
}
}
}
],
"ok" : 1.0
}