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Question regarding result persistence and restarting failed flows:

I have a flow that resembles this that I am running locally and on kubernetes
```@flow
def demo_flow(x=1):
    val = task_1(x)
    val = task_2(val)
    val = task_3(val)
    val = task_4(val)
    val = prone_to_fail_task(val)
    return val```
If expensive_prone_to_fail_task fails, I want to be able to restart my flow and have it retry just `prone_to_fail_task`  again. What do I need to achieve that? Will adding `cache_key_fn=task_input_hash,` to just `task_4` be sufficient?

I'm getting this error currently when trying to restart from the UI

```    raise MissingResult(
prefect.exceptions.MissingResult: State data is missing. Typically, this occurs when result persistence is disabled and the state has been retrieved from the API.)```

I think you need to configure your result storage appropriately

See the relevant docs page here
<https://docs.prefect.io/concepts/results/#result-storage-location>