https://www.mongodb.com/docs/manual/core/query-plans/
https://www.mongodb.com/docs/manual/reference/explain-results/
https://www.mongodb.com/docs/manual/tutorial/analyze-query-plan/

https://www.mongodb.com/docs/manual/administration/analyzing-mongodb-performance/#locking-performance

https://www.mongodb.com/docs/manual/tutorial/manage-the-database-profiler/
https://www.mongodb.com/docs/manual/reference/database-profiler/
    !!! results descr !!!
        https://www.mongodb.com/docs/manual/core/capped-collections/
            fixed-size for high-thouput
    The database profiler writes data in the system.profile capped collection
        "planCacheKey"
        "planSummary" : "IXSCAN { a: 1, _id: -1 }",
        ...
        "locks"
        ...
        "ts" : ISODate("2019-01-14T23:33:01.806Z"),
        "client" : "127.0.0.1",
        "appName" : "MongoDB Shell",
        "allUsers" : [{"user" : "someuser", "db" : "admin"}],
        "user" : "someuser@admin"
    https://www.mongodb.com/docs/manual/reference/system-collections/#mongodb-data--database-.system.profile

query-shape
    https://www.mongodb.com/docs/manual/reference/glossary/#std-term-query-shape
    A combination of query predicate, sort, projection, and collation.
    query-hash
    https://www.mongodb.com/docs/manual/release-notes/4.2/#std-label-4.2-query-hash
planCache
    https://www.mongodb.com/docs/manual/reference/operator/aggregation/planCacheStats/

options
https://www.mongodb.com/docs/manual/reference/configuration-options/#mongodb-setting-operationProfiling.slowOpThresholdMs
    slow-op-log
    https://www.mongodb.com/docs/manual/reference/configuration-options/#operationprofiling-options

https://www.mongodb.com/docs/manual/reference/method/db.getProfilingStatus
    db.getProfilingStatus()
https://www.mongodb.com/docs/manual/reference/method/db.setProfilingLevel/
    (0) - disable

sample
  COLSCAN-bad, IXSCAN-good
https://www.mongodb.com/docs/manual/reference/method/db.collection.explain
    db.runCommand({explain: { 'find' : 'collection', 'filter' : { 'brandId' : { '$eq' : 'BRND' } }, 'skip' : 0, 'limit' : 0, 'maxTimeMS' : 60000 }})
    db.collection.find({"brandId":{"$eq": "BRND"}}).explain()
    db.collection.explain().find().help()
    .find(...).explain("executionStats")
        https://www.mongodb.com/docs/manual/tutorial/analyze-query-plan/

!!!
You can use $comment to add data to the query predicate to make it easier to analyze data from the profiler.
https://www.mongodb.com/docs/manual/reference/operator/query/comment/#mongodb-query-op.-comment
    db.setProfilingLevel(2, 0)
    db.collection.find( { <query>, $comment: <comment> } )
    then -> "comment": "val"

! query plan cache commands
https://www.mongodb.com/docs/manual/reference/command/nav-plan-cache/
!!! cursor.hint
https://www.mongodb.com/docs/manual/reference/method/cursor.hint/#mongodb-method-cursor.hint

from-java-driver
https://www.mongodb.com/docs/drivers/java/sync/current/fundamentals/crud/read-operations/cursor/