MongoDB 3.4.0-rc1 has been released for testing purposes, addressing several issues including SERVER-19153, where the $match operator is pushed conditionally before $project, and WT-2831, where creating a checkpoint can be skipped if there have been no changes. The release also includes fixes for other issues such as rejecting unknown options in the Create command and improving the progress meter for initial sync collection clone operations. This release candidate marks the culmination of the 3.4.x development series, with new features and improvements available for testing before the final version is released.