The .explain() method in the shell works with some write methods (update, remove, findAndModify), but it doesn't work with the newer CRUD API.

The missing explain methods are:

"deleteMany",
"deleteOne",
"findOne",
"findOneAndDelete",
"findOneAndReplace",
"findOneAndUpdate",
"insertMany",
"insertOne",
"replaceOne",
"updateMany",
"updateOne"

I think this would be especially helpful for new hires: explain is a good way to quickly find the code that implements a command.