The context of the question is Secrets management.
As the title says, how do you change a secret that half of your production applications use right now?
What did you try? @030, I've tried out Hashicorp's Vault and recently tried AWS Parameter store. Could you clarify the question of what you mean by 'half of your production applications use right now' ? Are you looking for a way to update only half of your production apps and leave the others as they are, or are you saying you have configs in production that don't match each other and you would like to force a consistence usage of secrets across all of the apps?