MongoDB driver slow performance for node.js - node.js

Question

I have an issue with slow data fetch. I have the following query to fetch the data
const query1 = this._ctx.signals.find({
user_id: user._id,
'spell.id': null,
'metadata.0.spell_id': { $in: spellsIds }
}).hint({user_id: 1, 'spell.id': 1, 'metadata.0.spell_id': 1}).explain('allPlansExecution')
And the execution time according to explain is 35ms. Here is explain object
{
queryPlanner: {
plannerVersion: 1,
namespace: 'gringotts.Signals',
indexFilterSet: false,
parsedQuery: { ... },
winningPlan: {
stage: 'FETCH',
inputStage: {
stage: 'IXSCAN',
keyPattern: {
user_id: 1,
'spell.id': 1
},
indexName: 'user_id_1_spell.id_1',
isMultiKey: false,
multiKeyPaths: {
user_id: [],
'spell.id': []
},
isUnique: false,
isSparse: false,
isPartial: false,
indexVersion: 2,
direction: 'forward',
indexBounds: { ... }
}
},
rejectedPlans: []
},
executionStats: {
executionSuccess: true,
nReturned: 23866,
executionTimeMillis: 35,
totalKeysExamined: 23869,
totalDocsExamined: 23866,
executionStages: {
stage: 'FETCH',
nReturned: 23866,
executionTimeMillisEstimate: 1,
works: 23869,
advanced: 23866,
needTime: 2,
needYield: 0,
saveState: 23,
restoreState: 23,
isEOF: 1,
docsExamined: 23866,
alreadyHasObj: 0,
inputStage: {
stage: 'IXSCAN',
nReturned: 23866,
executionTimeMillisEstimate: 1,
works: 23869,
advanced: 23866,
needTime: 2,
needYield: 0,
saveState: 23,
restoreState: 23,
isEOF: 1,
keyPattern: {
user_id: 1,
'spell.id': 1
},
indexName: 'user_id_1_spell.id_1',
isMultiKey: false,
multiKeyPaths: {
user_id: [],
'spell.id': []
},
isUnique: false,
isSparse: false,
isPartial: false,
indexVersion: 2,
direction: 'forward',
indexBounds: { ... },
keysExamined: 23869,
seeks: 3,
dupsTested: 0,
dupsDropped: 0
}
},
allPlansExecution: []
},
serverInfo: {
host: 'ip-192-168-1-98.ec2.internal',
port: 27017,
version: '4.4.4',
gitVersion: '8db30a63db1a9d84bdcad0c83369623f708e0397'
},
ok: 1
}
When I try to fetch data with the following piece of code I have execution time starting from 750ms to 900ms (21x). Average document size is 544.6135124888154 bytes.
console.time('q1-time')
const q1 = await this._ctx.signals.find({
user_id: user._id,
'spell.id': {
$in: spellsIds
}
// #ts-ignore
}).hint({
user_id: 1,
'spell.id': 1
})
const f = (q) => {
const result = []
return new Promise((res, rej) => {
q.stream().on('end', function() {
console.log('done processing stream')
res(result)
})
q.stream().on('data', (d) => {
result.push(d)
})
})
}
const data = await f(q1)
console.timeEnd('q1-time') -- > q1 - time 769.511 ms
I tried different approaches: .toArray, iteration via cursor and the one with streams (I posted above) is the fastest).
Why it takes so much longer to get the data? Can it be optimized somehow?