Updating Rails: where's a memcache gone?

Can you imagine that updating a Rails version may become a real chase for performance? Keep reading to know the whole story.The first tryThings started to go weird one morning when I have deployed my pull-request updating Rails version from 5.0 to 5.1 (tested both locally and on staging environment) to production. Everything went pretty well in terms of functionality until I discovered that the application works slower and slower as the request rate increases. I decided to take a break and rolled back to the previous release.Here’s how the NewRelic’s application performance chart looked like:.