replset [primary] test> var changeStream = db.watch()
ChangeStreamCursor on test
replset [primary] test> db.foo.insert({name:"John"})
DeprecationWarning: Collection.insert() is deprecated. Use insertOne, insertMany, or bulkWrite.
{
  acknowledged: true,
  insertedIds: { '0': ObjectId("60ec1c6464ec76b1492fae72") }
}
replset [primary] test> changeStream.next()
Warning: If there are no documents in the batch, next will block. Use tryNext if you want to check if there are any documents without waiting.

replset:PRIMARY> var changeStream = db.watch()
replset:PRIMARY> db.foo.insert({name: "foo"})
WriteResult({ "nInserted" : 1 })
replset:PRIMARY> changeStream.next()
{
	"_id" : {
		"_data" : "8260EC1C9E000000012B022C0100296E5A1004627EABB2BF0E4DDB8D434E0CB526A8B046645F6964006460EC1C9E42E74AB99614C8460004"
	},
	"operationType" : "insert",
	"clusterTime" : Timestamp(1626086558, 1),
	"fullDocument" : {
		"_id" : ObjectId("60ec1c9e42e74ab99614c846"),
		"name" : "foo"
	},
	"ns" : {
		"db" : "test",
		"coll" : "foo"
	},
	"documentKey" : {
		"_id" : ObjectId("60ec1c9e42e74ab99614c846")
	}
}