Continuous admin.$cmd queries in slowest operations


we are facing one strange issue in the Realtime Slowest operations. It seems that for every docker that connects to mongoDB we have one or more continuous admin.$cmd commands that are reading some thousands of documents.

All our dockers are NodeJS projects accessing the database via mongoose. One sample of the JSON RESPONSE is:

op: command
locks: Object
lockStats: Object
waitingForFlowControl: false
microsecs_running: 8432221
currentOpTime: 2021-06-09T12:02:02.646+00:00
secs_running: 8
waitingForLock: false
flowControlStats: Object
type: op
active: true
opid: 34729718
ns: admin.$cmd
numYields: 0
waitingForLatch: Object
  timestamp: Object
    $date: 2021-06-09T12:01:54.314Z
  captureName: FutureResolution
connectionId: 55945
clientMetadata: Object
  driver: Object
    name: nodejs|Mongoose
    version: 3.6.6
  os: Object
    type: Linux
    name: linux
    architecture: x64
    version: 5.4.0-1032-azure
  platform: 'Node.js v10.15.3, LE (unified)
  version: 3.6.6|5.12.5
desc: conn55945
client: xx.xx.xx.xx:49380
query: Object
  $db: admin
  ismaster: true
  maxAwaitTimeMS: 10000
  topologyVersion: Object
    processId: Object
      $oid: 60bd2bb49561137ee56a1868
    counter: 8
$clusterTime: Object
  clusterTime: Object
    $timestamp: Object
      t: 1623235570
      i: 2
  signature: Object
    hash: Object
      $binary: Object
        base64: /YEfTf0O9ucqS31QdgoFKDLo0qg=
        subType: 00
    keyId: 6914106613016035000

We are using MongoDB version 4.4.6.

Do you have an idea on what type of activity the system is performing?