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Note on Evolving API: a concern raised on KIP-591 about having such an interface is that the increased API surface area would mean introducing new store implementations would cause custom state store implementations to throw compile time errors. Introducing the *Parameters Params classes will prevent such issues unless an entirely new store type is added.

If an entirely new state store type (beyond KV/Windowed/Session) is added - I think it is valid to have new store types have a default implementation that throws new UnsupportedOperationException() as it is unlikely that users that specify a custom state store as the default will want a different (e.g. ROCKS_DB) store created without them knowing. This also seems unlikely since these three have been there for many years and they've been the only three for that duration.