Ruby keeps amazing me! Did you know it has not one, but two databases built right into its standard library? Okay, the two are basically the same under the hood, but still!
When you write a Ruby script, it's not unusual that you come to the point where you want to persist some data, so that when you run the script the next time, it can access that data from the previous run. Examples are the result of an API call you don't need to execute every single time the script runs, configuration values that rarely change, or a timestamp of the last time a certain action was performed.