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Not sure I agree with this. In your original post, if you had changed the sentence

```
However the KeepAlive also has another design issue: both the fetch manager and the datastore need to know how often they each expect it to be called, which is a somewhat awkward contract.
```

Into

```
However the KeepAlive also has another design issue: the fetch manager and the datastore share some configuration variables.
```

that might have worked better. When you make that change, it makes it easier to see that this is a fairly minor concern you are addressing. I don't think that sharing a configuration variable makes it so that the "concerns aren't too well separated" in the code. Further, there is no performance problem with using KeepAlive even with the in-memory use-case you're describing. If this was actually a use-case we had today (which, as yet, it is not), the performance impact would be somewhere between negligible and nonexistent depending on how the user configured walker.

I don't really have a problem with the proposed change, it would take maybe a day to implement. Dan if you would like me to implement that, let me know, I'll execute on it.