The current read concern default for sharded secondary reads (that are not associated with a causally consistent session) is 'available' and in all other cases is 'local'. Starting in 5.0, we plan to change the default read concern to always be 'local'.

Summary

Review the current read and write concern settings and propose changes to provide more intuitive and safe defaults.

Motivation

There are two primary motivations for adjusting our defaults. First, although MongoDB allows users to choose the right tradeoff between performance and consistency, the nuances of the system are complex and are often misused, or surprising to users. We should provide more intuitive and stronger consistency default settings out of the box. Second, MongoDB has battled with the user perception that it is not reliable or intentionally chooses unsafe defaults to appear faster in benchmarks. By changing the defaults, we eliminate that argument.

Cast of Characters

• Product Owner:
• Project Lead:
• Program Manager:
• Drivers Contact:

Documentation

Scope Document
Technical Design Document
Product Description