MongoDB .explain("executionStats") shows keysExamined of something around 103,000 but I cant find out what it means.
Santiago Trujillo
From MongoDB docs:
explain.executionStats.totalKeysExamined
Number of index entries scanned.
totalKeysExaminedcorresponds to thenscannedfield returned bycursor.explain()in earlier versions of MongoDB.
This are good news when you have totalKeysExamined > 0 , this mean your query is using index. Here it is important to understand what is the size of your database , index selectivity , frequency and use case of this query to be identified if 103,000 is a good examination number for your search.
If you have totalKeysExamined = 0 , and totalDocsExamined > 0 than you may need to create some indexes.
The best case is when you have totalDocsExamined = 0 and totalKeysExamined > 0 , this is the case when you have the so called "covered query" , this is the fastest case where you search and load only from the index in memory and do not touch the rest part of the documents from storage.