You can delete with safety the index with name .opendistro-alerting-alert-history when is older than 1Month?
Hi @maybe_yes, you can delete any of the roll over indices, the current history index is where alerts are stored that do not meet the roll over period.
For example lets say you had an event about 2 hours ago and the monitor created an alert, then later the issue was resolved and the alert moved to the COMPLETED state. In this case the alert will be stored in this index until the next roll over period which by default is 24 hours. So I do not recommend deleting it unless you will no longer be using alerting.