Telemetry in Ruby Part 1: Metrics and Storage

Adding feature flags is easy but deleting them requires care and safety. We even mess it up. Before you delete a flag, you have to remove it from the code. If you don't remove it from the code, deleting a flag is the same as disabling it.But even after removing all the uses in the code, deleting a flag is still nerve-wracking. It's like dropping a column or table in production. Even when you've triple checked, you throw up a bit in your mouth as you hit on the command or click the button.When cleaning up a feature flag, you need answers to these questions:What is the state of this flag in key environments?Did I remove all the uses of the flag from the code?Is this flag still being used anywhere?Am I deleting the right flag?.