Mongo Performance check and tune

mongoperf.md

Check profileing status:

db.getProfilingStatus()
db.getProfilingLevel()

More information: https://docs.mongodb.com/manual/tutorial/manage-the-database-profiler/

Find slow queries: https://gist.github.com/rantav/3433277

Test replay with https://github.com/ParsePlatform/flashback

https://docs.mongodb.com/manual/reference/method/db.collection.getPlanCache/#db.collection.getPlanCache
Query cached

Notice that each db has separated profiler, so remember to set for all databases.

Mongo 2.6 build index in background of primary, then all secondaries.

Try to split read and write. It is better for debugging and finding slow queries.