Mongodb 4.0 bulkWrite is extremely slow while updating - node.js

Question

I have a collection with more than 1 million user, I'm trying to update
users balance on some event.
while I'm trying to update e.g. 299 row it takes up to 15739.901ms
no high load on the sever, it's just mongo running. I'm storing the database on an SSD Samsung evo 860 but MongoDB installed on an HDD.
Here's my function:
async usersUpdate(usersToUpdate){
const updates = [];
return new Promise(async (resolve, reject) => {
users.forEach(user=>{
updates.push(
{ "updateOne": {
"filter": { "userID": user.userID, 'balance':user.userBalance },
"update": { "$set": { "user.$.userBalance": user.newBalance } , "$addToSet":{'orders.$.orderID':user.OrderID} }
}
});
}
console.log('total updates' , updates.length);
if (updates.length > 0){
const DbConnection = await getConnection();
const usersTable = DbConnection.collection('usersCollection');
transactionsTable.bulkWrite(updates, {"ordered": false, writeConcern : { w : 0 } }, function(err, result) {
// do something with result
if (err) return reject(err);
return resolve(result)
});
}else{
return resolve('Nothing to update');
}
});
}
both userID and userBalance are indexed, and I set writeconcern equals to false.
I don't know what's the wrong with code and why it's super slow.
What's the problem and how could I speed up the progress a bit?
Mongodb config file:
storage:
dbPath: "/ssd/mongodb"
journal:
enabled: false
Explain result:
{ queryPlanner:
{ plannerVersion: 1,
namespace: 'usersDB.usersCollection',
indexFilterSet: false,
parsedQuery:
{ '$and':
[ { userID:
{ '$eq': 'Kfasg3ffasg' } },
{ 'user.userBalance': { '$eq': 10 } } ] },
winningPlan:
{ stage: 'FETCH',
filter: { 'user.userBalance': { '$eq': 10 } },
inputStage:
{ stage: 'IXSCAN',
keyPattern: { userID: 1 },
indexName: 'userID_1',
isMultiKey: false,
multiKeyPaths: { userID: [] },
isUnique: true,
isSparse: false,
isPartial: false,
indexVersion: 2,
direction: 'forward',
indexBounds:
{ userID:
[ '["Kfasg3ffasg", "Kfasg3ffasg"]' ] } } },
rejectedPlans: [] },
executionStats:
{ executionSuccess: true,
nReturned: 1,
executionTimeMillis: 24,
totalKeysExamined: 1,
totalDocsExamined: 1,
executionStages:
{ stage: 'FETCH',
filter: { 'user.userBalance': { '$eq': 10 } },
nReturned: 1,
executionTimeMillisEstimate: 0,
works: 2,
advanced: 1,
needTime: 0,
needYield: 0,
saveState: 0,
restoreState: 0,
isEOF: 1,
invalidates: 0,
docsExamined: 1,
alreadyHasObj: 0,
inputStage:
{ stage: 'IXSCAN',
nReturned: 1,
executionTimeMillisEstimate: 0,
works: 2,
advanced: 1,
needTime: 0,
needYield: 0,
saveState: 0,
restoreState: 0,
isEOF: 1,
invalidates: 0,
keyPattern: { userID: 1 },
indexName: 'userID_1',
isMultiKey: false,
multiKeyPaths: { userID: [] },
isUnique: true,
isSparse: false,
isPartial: false,
indexVersion: 2,
direction: 'forward',
indexBounds:
{ userID:
[ '["Kfasg3ffasg", "Kfasg3ffasg"]' ] },
keysExamined: 1,
seeks: 1,
dupsTested: 0,
dupsDropped: 0,
seenInvalidated: 0 } },
allPlansExecution: [] },
serverInfo:
{ }