Improving performance on the logbook (or at least understanding it)

Getting the events from the beamline or ESRF logbook took ~7 seconds. I'd expect much faster as the fields are indexed:

const [total, events] = await Promise.all([this.count(find), Event.find(find).populate("tag").sort(sort).skip(skip).limit(limit).lean()]);

https://gitlab.esrf.fr/icat/icat-plus/-/blob/2.20/app/controllers/helpers/helper.logbook.controller.js#L156

The explain returns (and seems find to me):

{
  queryPlanner: {
    plannerVersion: 1,
    namespace: 'icatplus.events',
    indexFilterSet: false,
    parsedQuery: { '$or': [Array] },
    winningPlan: { stage: 'SUBPLAN', inputStage: [Object] },
    rejectedPlans: []
  },
  executionStats: {
    executionSuccess: true,
    nReturned: 100,
    executionTimeMillis: 2,
    totalKeysExamined: 100,
    totalDocsExamined: 100,
    executionStages: {
      stage: 'SUBPLAN',
      nReturned: 100,
      executionTimeMillisEstimate: 0,
      works: 101,
      advanced: 100,
      needTime: 0,
      needYield: 0,
      saveState: 0,
      restoreState: 0,
      isEOF: 1,
      inputStage: [Object]
    },
    allPlansExecution: []
  },
  serverInfo: {
    host: 'icat-database',
    port: 27017,
    version: '4.4.10',
    gitVersion: '58971da1ef93435a9f62bf4708a81713def6e88c'
  },
  ok: 1
}