Some tools let you pass a parameter to indicate that you only want the request to take effect if the requested resource is in some specific state. For example, Google Cloud Storage uses headers to allow you to set preconditions that must be met before the action takes place. For DELETEs you can use this to say "delete this resource but only if its generation (sort of a timestamp) is exactly $foo", where $foo is the generation last known to the client.

https://cloud.google.com/storage/docs/request-preconditions