This feature release of the Ruby Driver adds support for MongoDB server 5.1.

This release includes the following new features:

• RUBY-2524 Snapshot reads. Added new readConcern level "snapshot" (non-speculative) for read commands outside of transactions, including on secondaries.
• RUBY-2526 Support $merge and $out executing on secondaries
• RUBY-2659 Support 'let' option for aggregate command
• RUBY-2821 Support 'let' option for CRUD commands

This release removes support for Ruby versions 2.3 and 2.4. The minimal required Ruby version is now 2.5. Read more about this change here.

This release also removes support for MongoDB versions older than 3.6. Read more about this change here.

The following bugs were fixed:

• RUBY-2805 Push monitor thread can exit when address resolution fails

The following non-breaking changes were made:

• RUBY-2806 Avoid tight looping in push monitor
• RUBY-2733 mapReduce command is now deprecated