core.cache TTL cache expiration visibility between lookup and has?

The documented TTL cache type in clojure.core.cache associates each entry with an expiration threshold. The unresolved behavior is whether expiration is implemented as eager eviction or as a lazy filter applied on lookup, and how that choice is exposed by the cache API.

The decision matters for consistency across access paths. A read-through helper typically recomputes only on a cache miss, so any difference between lookup semantics and presence checks can lead to divergent freshness guarantees. Behavior is version-sensitive across core.cache releases and may differ from memoization wrappers built on top of it.

For a pinned core.cache version using ttl-cache-factory, does lookup return nil for an expired entry while has? still reports the key as present? Does a through-cache style read-through treat an expired entry as a hit or a miss? Which API surface should be used as the authoritative freshness check?