A few minutes ago, I was going crazy over a bug caused due to data mutation in Rails.

Basically, user1 was creating a post record and it's stored in the database normally however, on page reload for a second user, user2, the post (that user1 created) was update to belong to user2. This is because, on page reloads, I was using `<<` method call to append user2 and user1 posts together! Apparently, `<<` not only mutates the array, it also performs a database update.

Kill me please!!

Also, data immutability seems a more reasonable feature in languages now.