[Question] evaluation key storage time to live

[va1eb]

I tried example deployed on my server with real client and I can see that the client is not trying to store a new key using /key EP when the /queries endpoint is failing with 400 code (due to key not found error).
From the sources I see that it is required to store the key and there is a comment saying that the key size can be up to 10 MiB.
The evaluation key storage key contains User-Identifier header value (which is Pseudorandom identifier tied to a user), it is unclear is the value static for the user or it can change in certain circumentences.
Having that it looks like I have to store the evaluation key forever, but since user can try the application and never be back, and I never know this - there is a big probability I store a lot of unused data which will be a waste of my storage.

I could store the key with ttl equal to 1 month (for example) and update the ttl each time the client try to access the key but I believe there can be cases when the client try accessing /queries endpoint after the key is deleted from storage.

Could you please provide me with the answers for the following questions:

Is there any way to enforce the client to recreate and store a new key by returning a specific status code from /queries EP?
Is there any recommendation about evaluation key time to live?
Is it possible to implement logic to recreate the evaluation key in client code?

[karulont]

Is there any way to enforce the client to recreate and store a new key by returning a specific status code from /queries EP?

Yes, there is: You have to return a non 200 status code, and the response body should be a serialized Error with the error type set to EvaluationKeyNotFound

Is there any recommendation about evaluation key time to live?

The device will rotate User-Identifier value every week, so there is no need to store an evaluation key for longer than that.
Also there is no need to update TTL of a evaluation key upon access. You can set it to a week when it is uploaded.

The system guarantees that it will not reuse a User-Identifier for longer than a week.

Is it possible to implement logic to recreate the evaluation key in client code?

Currently there is no API you can call that will force the system to recreate the evaluation key.

[karulont]

Yes, there is: You have to return a non 200 status code, and the response body should be a serialized Error with the error type set to EvaluationKeyNotFound

That sounds like something that the example service should start doing anyway. I filed #102 some time ago.

[va1eb]

Thanks a lot