Django annotate with dynamic value

Hi in my model i have property that fully is in cache, not in database

class Model(models.Model):

    def _get_last_seen_cache_name(self) -> str:
        return f'{self.hostname.upper()}_last_seen'

    def last_seen(self) -> datetime | None:
        cached = cache.get(self._get_last_seen_cache_name, None)
        if isinstance(cached, datetime):
            return cached
        return None

    def update_last_seen(self) -> None:
        cache.set(self._get_last_seen_cache_name, get_now().replace(microsecond=0), None)

How can i annotate with this value last_seen queryset. Want use sorting on this column in admin page. But for this, i need get values from cache on annotation, execute cache.get() with proper key name. Something like this, not working example:

queryset = super().get_queryset(request)
queryset = queryset.annotate(last_seen=Value(cache.get(Concat('hostname', Value('_last_seen')))), CharField()))


queryset = queryset.annotate(last_seen=Value(cache.get(f"{F('hostname')_last_seen}")), CharField()))

I can annotate with literal value, but how annotate with dynamic value, that doesnt exist in database, but in cache or in memory only? How to do hostname substitution in a function?

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