MongoDB has a nested param structure for readPreference and writeConcern. This also is required when using Criteria#with() method:

MyModel.with(read: { mode: :primary })
MyModel.with(write: { w: :majority, j: 1, wtimeout: 10 })

This syntax awkward. It would be nicer if we could just do:

MyModel.read_mode(:primary)      # or read_preference()
       .write_concern(:majority) # or write_w(), write_ack()
       .write_journal(1)
       .write_timeout(10)

Also as args to with() method:

MyModel.with(read_mode: :primary, write_concern: :majority, ...)

There is some concern (pun intended) that these names could be used by MongoDB server parameters in the future, but I think it's pretty unlikely and there is already some precedent for flat-usage of these parameters in MongoDB Connection String URIs