Rails 4.0Rails 4.0 introduced the following changes: 1. Thread safety is enabled by default. 2. Strong Parameters were added for mass assignment protection. 3. Turbolinks was added to speed up page loads by preventing full page reloads. 4. Russian Doll Caching was introduced to maximize cache hits by nesting fragment caches. Some features were extracted to gems including Action and Page Caching, Active Res
