More at rubyonrails.org:

Ruby on Rails 6.1 Release Notes

Highlights in Rails 6.1:

  • Per-database Connection Switching
  • Horizontal Sharding
  • Strict Loading Associations
  • Delegated Types
  • Destroy Associations Async

These release notes cover only the major changes. To learn about various bug fixes and changes, please refer to the changelogs or check out the list of commits in the main Rails repository on GitHub.